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Religion  and  Chemistry 


A  RE-STATEMENT  OF  AN  OLD  ARGUMENT 


JOSIAH  PARSONS  COOKE 

Erving  Professor  of  Chemistry  and  Mineralogy  in  Harvard  University 


|-f 


A     NEWLY   REVISED    EDITION 


Duo  si^nt  <^a^  in  ccgnit^i&iem  Dei  dvLtiat  Creatura  et  Scriptura 


y1 


'x'i 


St.  Augustine 


NEW  YORK 
CHARLES    SCRIBNER'S    SONS 

743  AND  745  Broadway 
1880 


Copyright,  1864,  by 
PETER    G.   TAYLOR 

Copyright,  1880,  by 
JOSIAH    P.    COOKE 


PRES9  OF  J.  i.  LITTLE  &  CO., 
H03.  10  TO  20   ASTOR   PLACE,  NEW  VORK. 


THE  FIRST  EDITION  OF  THIS  BOOK   WAS   DEDICATED 
TO  A  GREATLY  BELOVED  FATHER. 

THIS  ONE  IS    CONSECRATED    BY  THE  MEMORIES 

OF  HIS  LONG  AND   HONORABLE  LIFE, 

PEACEFULLY   CLOSED. 


PREFACE. 


The  conditions  under  which  this  work  was  first 
published  are  stated  in  the  preface  to  the  first 
edition,  reprinted  below.  Although  the  book  has 
been  long  out  of  print,  the  author  has  not  been  able 
to  revise  it  for  a  new  edition  until  now,  and  returning 
to  this  work  of  his  youth,  after  twenty  years  of  active 
life,  he  has  found  nothing  in  the  tone  or  sentiments 
of  the  book  which  he  desired  to  change.  Indeed, 
larger  knowledge  has  only  served  to  confirm  the  gen- 
eral convictions  therein  expressed.  But,  of  necessity, 
the  discovery  of  new  facts  and  changes  in  scientific 
theories  have  required  alterations  of  phraseology  in 
many  places,  and  more  experience  has  led  to  greater 
caution  in  the  statement  of  conclusions.  It  was  the 
author's  first  intention  to  re-write  the  whole  book  on 
a  different  plan,  and  in  retaining  the  popular  style  of 
the  first  edition  he  has  yielded  to  the  judgment  of 
friends  who  thought  that  the  book  would  be  more 
useful  in  its  early,  fresh  form.     The  discussion  of  the 


VI  PREFACE. 

principles  of  crystallography  in  the  first  edition  has 
been  omitted  in  the  revision,  because  found  too 
abstruse  for  popular  reading  ;  but  the  place  has  been 
more  than  supplied  by  the  new  matter  which  has 
been  added.  The  work  is  solely  a  popular  expo- 
sition of  the  subjects  on  which  it  treats,  and  this 
design  has  precluded  a  fuller  discussion  of  many 
points,  as  well  as  that  precision  of  statement  which 
might  be  expected  in  a  more  formal  essay.  By 
vote,  recorded  in  their  proceedings  of  March  6,  1875, 
the  Directors  of  the  Brooklyn  Institute  released  to 
the  author  their  copyright  in  the  original  work,  and 
he  would  here  express  his  grateful  appreciation  of 
this  courtesy. 

Newport,  September '^o,  1880. 


PREFACE  TO  THE  FIRST  EDITION. 


The  lectures  now  published  were  first  delivered 
before  the  Brooklyn  Institute  on  Sunday  evenings 
of  January  and  February,  1861,  and  the  larger 
part  of  them  were  subsequently  repeated,  during 
the  same  winter,  before  the  Lowell  Institute  in 
Boston,  and  before  the  Mechanics*  Association  of 
Lowell.  The  progress  of  science  since  that  time 
has  rendered  necessary  many  additions,  and  in  re- 
vising the  lectures  for  publication,  the  material 
has  been  thus  so  greatly  increased  that  what  was 
originally  prepared  and  delivered  as  six  lectures  is 
now  distributed  over  ten.  At  the  time  when  the 
lectures  were  written,  Mr.  Darwin's  book  on  the 
Origin  of  Species,  then  recently  published,  was  ex- 
citing great  attention,  and  was  thought  by  many 
to  have  an  injurious  bearing  on  the  argument 
for  design.  It  was,  therefore,  made  the  chief  aim 
of  these  lectures  to  show  that   there   is   abundant 


Vlll  PREFACE. 


evidence  of  design  in  the  properties  of  the  chemi- 
cal elements  alone,  and  hence  that  the  great  argu- 
ment of  Natural  Theology  rests  upon  a  basis  which 
no  theories  of  organic  development  can  shake.  In 
illustrating  his  subject,  the  author  has  used  freely 
all  the  materials  at  his  command,  and  if,  in  any 
case,  he  has  failed  to  give  due  acknowledgment,  it 
has  been  because  by  long  dwelling  on  the  subject 
the  thoughts  of  others  have  become  blended  with 
his  own.  He  would  here  acknowledge  his  repeated 
indebtedness  to  Professor  Guyot's  work  on  "  Earth 
and  Man,'*  to  Professor  Faraday's  published  Courses 
of  Elementary  Lectures,  and  to  Professor  Tyn- 
dalFs  Lectures  on  "  Heat  considered  as  a  Mode  of 
Motion."  He  would  also  express  his  especial  obli- 
gations to  the  author  of  "  In  Memoriam,"  in  whose 
verses  he  has  discovered  a  truer  appreciation  of 
the  difficulties  which  beset  the  questions  discussed 
in  this  volume,  than  he  has  ever  found  in  the  phi- 
losophy of  the  schools. 

Cambridge,  May  3d,  1864. 


CONTENTS. 


CHAPTER.  PAGES 

I.     Statement  of    the   Case — Testimony    of  the 

Atmosphere 1-30 

II.     Testimony  of  the  Atmosphere — Concluded 31-68 

III.     Testimony  of  Oxygen 69-94 

IV.     Testimony  of  Oxygen — Concluded 95-118 

V.     Testimony  of  Water 119-162 

VI.     Testimony  of  Carbonic  Dioxide .* 163-202 

VII,     Testimony  of  Nitrogen 203'-228 

VIII,     Argument  from  Special  Adaptations 229-257 

IX.    Argument  from  General  Plan 258-292 

X.     Necessary  Limitations  of  Scientific  and  Re- 
ligious Thought 293-332 

ix 


^    L  i  H  H  A  a  V 

UNIVKS^^^TY   OF 

CALmJivNlA.^ 


RELIGION  AND  CHEMISTRY. 


CHAPTER      I. 

STATEMENT    OF    THE    CASE— TESTIMONY    OF    THE 
ATMOSPHERE. 

The  time  has  been  when  the  Christian  .Church 
was  an  active  antagonist  of  physical  science ;  when 
the  whole  hierarchy  of  Rome  united  to  condemn  its 
results  and  to  resist  its  progress ;  when  the  immedi- 
ate reward  of  great  discoveries  was  obloquy  and 
persecution.  But  all  this  has  passed.  The  age  of 
dogmatism  has  gone,  and  an  age  of  general  scepti- 
cism has  succeeded.  The  power  of  traditional  au- 
thority has  given  place  to  the  power  of  ideas,  and 
physical  science,  which  before  hardly  dared  to  assert 
its  birthright,  and  could  even  be  forced  to  recant,  on 
its  knees,  its  demonstrated  truths,  has  now  become 
one  of  the  rulers  of  society.  By  its  rapid  growth, 
by  its  conquests  over  brute  matter,  and  by  its  won- 
derful revelations,  it  has  deservedly  gained  the 
highest  respect  of  man,  while  by  multiplying  and 
1  I 


THE   CHURCH   AND   SCIENCE. 


diffusing  the  comforts  of  life  it  has  become  his  ac- 
knowledged friend.  Every  effort  is  now  made  to 
further  its  progress.  Its  great  discoveries  win  the 
applause  of  nations,  and  its  fortunate  students  are 
remembered  when  the  princes  and  nobles  of  the 
earth  are  forgotten. 

All  this  is  well.  But  unfortunately,  elated  by  his 
success,  the  stripling  has  been  at  times  proud  and 
arrogant,  usurping  authority  not  his  due.  Forget- 
ting his  early  faith,  he  has  approached  with  irreverent 
thoughts  the  holy  temple  of  our  religion,  and,  not 
content  to  worship  in  the  outer  court,  has  dared  to 
penetrate  into  the  very  Holy  of  Holies,  and  apply 
his  material  tests  even  to  the  vessels  of  the  altar. 
No  wonder  that  the  Church  should  become  alarmed, 
that  many  of  her  best  men,  holding  fast  to  the 
sacred  dogmas  of  our  religion  as  the  only  sure 
anchor  of  their  faith  in  this  world,  and  their  sole 
ground  of  hope  for  the  next,  should  join  in  a  gen- 
eral cry  against  the  whole  tendency  of  science  and 
its  results. 

But  this  is  a  great  mistake.  Judging  of  the  real 
character  of  physical  science  from  the  pretensions 
of  a  few,  and  not  possessing  the  power  or  opportu- 
nity of  investigating  for  themselves,  these  good  men 
are  unnecessarily  alarmed :  the  phantom  they  fear  is 
purely  of  their  own  creation,  and,  could  they  but 
know  the  whole  truth,  they  themselves  would  see 
that  to  ignore  the  well-established  results  of  science, 
and  to  denounce  its  legitimate  tendency,  is  a  policy 
as  short-sighted  as  it  is  illiberal  and  unchristian. 
(    Fortunately,  such  fearful  souls  constitute  but  a 


THE   CHURCH   AND   SCIENCE. 


small  party  in  the  Christian  Church.  There  is  a  far 
nobler  and  more  courageous  faith  than  theirs, — a 
faith  so  strong  in  its  convictions  that  it  fears  no 
criticism,  however  searching,  and  no  scientific  analy- 
sis, however  rigorous  it  may  be, — a  faith  which  finds 
in  the  Bible,  not  a  series  of  dead  formulas,  but  a 
mass  of  living  truth, — a  faith  which  really  believes 
that  the  God  of  nature  is  the  God  of  grace,  and  that 
man  was  created  in  the  image  of  this  one  and  only  | 
God, — R  faith  which  wells  up  from  the  depths  of  the  ? 
soul,  which  speaks  because  it  believes,  which  believes 
because  it  feels, — a  faith  whose  sources  are  as  hid- 
den as  those  of  the  fountain,  but  whose  reality  is  as 
living  as  the  verdant  landscape  which  the  fountain 
-^-waters. 

It  is  the  men  with  a  faith  like  this  who  are  the 
really  brave  Christians.  They  are  not  alarmed  at  the 
apparent  contradictions  between  science  and  revela- 
tion. By  the  very  imperfections  of  their  own  facul- 
ties, which  they  so  keenly  appreciate,  they  have 
been  taught  that  mysteries  exist ;  nay,  they  find  in 
these  very  mysteries  the  strongest  bulwarks  of  their 
faith ;  for  they  feel,  with  Robert  Hall,  that  "  a  re-T^ 

ligion  without  its  mysteries  would  be  a  temple  withj 

out  its  God.'*  They  are  fully  assured  that  our  minds 
were  framed  after  the  likeness  of  their  Divine  origi- 
nal, in  order  that  we,  creatures  of  the  dust  though 
we  are,  might  nevertheless  in  our  feeble  measure 
comprehend  God's  workmanship  and  sympathize 
with  his  divine  thoughts ;  and  they  reject  as  absurd 
the  doctrine  that  man,  thus  created  an  intelligent 
and  sympathizing  observer  of  God's  universe,  should 


BRAVE   CHRISTIAN  FAITH. 


have  been  permitted,  in  the  legitimate  exercise  of 
the  very  powers  which  God  has  given  him,  to  build 
up  a  connected  system  of  science  in  direct  contra- 
diction to  those  higher  and  spiritual  truths  which 
the  Father  has  been  mercifully  pleased  to  reveal  to 
his  sinning  children  through  his  prophets  and  his 
Son. 

In  the  sight  of  this  brave  Christian  faith  there  can 
be  no  essential  contradiction  between  science  and 
revelation.  On  the  contrary,  all  nature  appears  ra- 
diant with  the  Divine  Presence. 

"  The  heavens  declare  the  glory  of  God,  and  the7~ 
firmament  showeth  his  handiwork.  Day  unto  day 
uttereth  speech,  and  night  unto  night  showeth 
;;.vlcnowledge.  There  is  no  speech  nor  language  where! 
their  voice  is  not  heard.  Their  line  is  gone  out! 
through  all  the  earth,  and  their  words  to  the  end  of 
the  world.*' 
^'  But  although  this  glorious  song  of  the  Psalmist 
has  been  chanted  through  the  ages  as  expressing  the 
all  but  universal  belief  of  thinking  men,  there  has 
always  existed  at  the  same  time  a  philosophy  which 
interpreted  the  facts  of  nature  in  a  very  different 
way,  and  within  the  last  few  years  this  philosophy 
has  become  more  than  ever  before  dogmatic  and 
aggressive.  For  the  present  we  waive  all  discus- 
sion of  the  fundamental  questions  which  material- 
ism raises.  With  the  increasing  experience  of  life, 
we  cling  ever  more  and  more  fondly  to  the  belief 
that  the  grand  thoughts  which  the  study  of  nature 
suggests  to  our  mind  are  the  manifestations  of  a 
Being  who  is  not  only  to  be  venerated  and  feared 


NO   NECESSARY  ANTAGONISM.  5 

but  also  whom  to  be  reverenced  and  loved.  We  be- 
lieve that  the  instructions  and  suggestions  of  nature 
are  the  voices  of  an  all-powerful  Friend,  who  knows 
our  capabilities  and  infirmities ;  who  sympathizes  in 
our  joys  and  our  sorrows,  and  who  can  be  touched 
in  our  aspirations  and  our  prayers ;  a  Creator  whose 
laws  can  not  be  broken,  and  whose  behests  must  be 
obeyed ;  but  also  a  Father  who  ever  watches  over 
his  children,  and  who  was  in  Christ  reconciling  the 
world  unto  himself. 

f  We  do  not,  of  course,  expect  to  reach  such  a  faith  ] 
( as  this  through  the  study  of  nature  alone.  It  comes 
not  from  the  observation  of  external  phenomena, 
but  through  the  affections  and  aspirations  of  the 
soul,  which  finds  in  the  Christian  revelation  that 
which  answers  to  its  needs  and  satisfies  its  cravings; 
Any  system  of  natural  theology  like  that  of  Paley, 
which  looks  for  its  evidences  solely  to  external  phe- 
nomena, is  of  necessity  defective  and  powerless. 
If  nature  could  rise  of  her  own  self  to  spiritual 
things,  there  would  have  been  no  necessity  for  a 
revelation.  Indeed,  the  attempt  to  establish  a 
spiritual  truth  by  the  evidence  of  material  phe- 
nomena, is,  mutatis  mutandis,  but  a  repetition  of 
the  error  of  Aristotle  and  his  school,  who  vainly 
sought  to  frame  a  system  of  natural  philosophy 
independently  of  observation.  The  only  satisfactory 
evidences  of  the  truths  of  Christianity,  indepen- 
dent of  the  historical  record,  are  to  be  found  in 
its  adaptation  to  the  spiritual  needs  of  men,  and  it 
is  such  evidences  of  design  alone  that  have  persuaded 
the  world. 


RELIGION  AND  CHEMISTRY. 


Nevertheless,  while  we  cannot  expect  to  prove  the 
fundamental  principles  of  Christian  theism  by  the 
evidences  of  material  nature,  it  seems  to  us  that  an 
advantage  may  be  gained  by  discussing  material 
phenomena  from  the  theistic  point  of  view.  The 
purely  mechanical  aspects  of  nature  are  now  so 
prominently  presented  by  ingenious  and  powerful 
writers  that  it  may  be  a  satisfaction  to  many  thought- 
ful Christians  if  it  can  be  shown  that  the  same  facts 
may  be  interpreted  in  a  very  different  way,  and  that 
these  facts  are  at  least  as  consistent  with  the  Chris- 
tian theory  of  the  origin  of  the  universe  as  with  the 
theory  of  the  materialist.  In  this  conclusion  the 
Christian  philosopher  may  securely  rest,  looking  for 
the  confirmation  of  his  inherited  faith  to  his  own 
spiritual  experience,  in  which  alone  convincing  evi- 
dence can  be  found,  according  to  the  Master's  prom- 
ise: "  If  any  man  will  do  his  will,  he  shall  know 
of  the  doctrine,  whether  it  be  of  God,  or  whether  I 
speak  of  myself." 

The  illustrations  of  the  attributes  of  God,  which 
may  be  drawn  from  the  constitution  of  matter,  are 
conveniently  divided  into  two  classes, — first,  those 
which  appear  in  the  adaptation  of  various  means  to 
a  particular  end,  and,  second,  those  which  are  to  be 
found  in  the  unity  of  plan  according  to  which  the 
whole  frame  of  nature  has  been  constructed.  The 
first  class  are  exhibited  by  the  properties  of  matter, 
the  second  by  the  so-called  physical  laws  and  forces. 

In  following  out,  then,  the  order  which  seems  to 
be  so  obviously  indicated  by  the  nature  of  the  case, 
I  shall  ask  you,  in  the  first  place,  to  study  with  me 


ARGUMENT   FOR  DESIGN. 


the  physical  condition  of  our  atmosphere,  and  the 
properties  of  the  various  materials  of  which  it  con- 
sists ;  and  I  am  sure  we  shall  not  fail  to  find  in  one 
and  all  abundant  evidence  of  the  wisdom,  goodness, 
and  power  of  God.  Having  thus  made  you  ac- 
quainted with  some  of  the  more  important  scientific 
facts  required  for  my  argument,  I  shall  next  direct 
your  attention  to  those  grander  demonstrations  of 
God's  wisdom  and  power  which  appear  in  the  great 
laws  and  forces,  by  which  the  whole  material  uni- 
verse is  upheld,  and  lastly  an  examination  of  the 
relative  limits  of  scientific  and  religious  thought  will 
form  an  appropriate  termination  for  the  course. 

The  argument  from  special  adaptations  which  lies 
at  the  basis  of  most  works  on  natural  theology  is 
condensed  by  Dugald  Stewart  into  two  simple 
propositions.  The  one  is,  "  that  everything  which 
begins  to  exist  must  have  a  cause ;  '*  the  other, 
"  that  a  combination  of  means  conspiring  to  a  par- 
ticular end  implies  intelligence.'*  To  these  might 
be  added  the  two  equally  clear  propositions  stated 
by  Dr.  Reid  :  first,  "  that  design  may  be  traced  from 
its  effects ;  "  second,  "  that  there  are  evidences  of 
design  in  the  universe."  I  do  not  at  present  intend 
to  discuss  the  logical  validity  of  this  argument,  or 
the  general  value  of  analogical  reasoning  which  it 
implies.  Such  discussions  belong  particularly  to  the 
province  of  metaphysics,  and  I  willingly  leave  them 
to  abler  hands.  It  will  be  my  chief  object  in  these 
lectures  to  bring  to  your  notice  a  few  of  the  num- 
berless indications  of  adaptation  in  the  materials  of 
our  atmosphere,  assuming  for  the  present  that  these 


S  ARGUMENT  FOR  DESIGN. 

adaptations  are  evidences  of  design,  and  therefore 
evidences  of  the  existence  of  a  personal  God,  in- 
finite in  wisdom,  absolute  in  power.  When  we  have 
thus  become  acquainted  with  some  of  the  facts  on 
which  the  argument  rests,  we  may  then  profitably 
consider  the  validity  of  the  reasoning,  at  least  so  far 
as  to  weigh  the  objections  which  modern  material- 
ism has  urged  against  it. 

It  must,  however,  be  constantly  borne  in  mind  that 
the  portion  of  the  subject  with  which  we  are  to 
deal  should  occupy  only  a  very  subordinate  position 
in  any  comprehensive  scheme  of  natural  theology. 
We  have  already  expressed  the  opinion  that  the 
only  conclusive  evidences  of  the  truth  of  Chris- 
tianity, apart  from  the  historical  record,  are  those 
based  on  its  adaptation  to  the  spiritual  wants  of 
men,  and  all  other  facts  are  secondary  to  this  great 
central  truth.  But  even  when  established  on  its 
broadest  basis,  I  would  not  press  the  arguments  of 
natural  theology  too  far. 

For  myself,  I  believe  that  the  facts  of  human 
nature  themselves  all  tend  to  prove  that  a  divine 
revelation  is  the  only  legitimate  basis  for  a  system 
of  religion,  and  that  an  historical  faith  based  on  a 
supernatural  revelation  is  the  only  religion  possible 
for  imperfect  humanity.  Indeed,  I  am  led  to  think 
we  find  evidence  of  the  goodness  of  our  Heavenly 
Father  in  the  very  circumstance  that  the  founda- 
tions of  all  knowledge  have  been  laid  in  such  ob- 
scurity that  no  unaided  human  intellect  can  wholly 
dispel  the  cloud  which  hides  the  Creator  from  our 
sight,— 


PROVINCE   OF  NATURAL  THEOLOGY.  9 

**  To  feel,  although  no  tongue  can  prove, 
That  every  cloud  that  spreads  above 
And  veileth  love,  itself  is  love." 

This  very  obscurity  humbles  the  pride  of  human 
learning,  and  raises  its  constant  warning  against 
that  intellectual  idolatry  which  would  substitute  its 
shallow  philosophy  for  the  simple  truth  as  it  is  in 
Jesus.  The  Bible  once  received,  science  can  furnish 
abundant  illustrations  of  the  attributes  of  the  Being 
therein  revealed  ;  but  even  with  all  the  illumination 
which  has  been  the  immediate  or  secondary  result  of 
Christianity,  man  is  hopeless  without  its  authority, 
and  I  would  not  give  the  slightest  shadow  of  sup- 
port to  that  irreverent  presumption  which,  guided 
by  what  it  calls  the  unaided  light  of  nature,  would 
construct  a  system  of  religion  out  of  passions,  in- 
tuitions, and  I  know  not  what  absurdity. 

But  still  it  must  be  remembered  that  the  Chris- 
tian revelation  does  not  prove  the  existence  of 
God ;  on  the  contrary,  it  appeals  to  a  belief  in  his 
being  that  already  exists  in  the  mind  of  man.  The 
Bible  opens  with  this  assumption.  The  first  line  as- 
serts that — 

"  In  the  beginning  God  created  the  heaven  and 
the  earth.'* 

And  the  Hebrew  name  of  God,  Jehovah  {I am  that! 
am),  is  itself  a  declaration  of  his  self-existent  being. 

With  all  men  a  belief  in  some  Almighty  Power 
overshadowing  their  being  grows  up  spontaneously 
in  the  heart,  they  know  not  how  ;  but  the  educated 
and  the  intelligent  seek  further  to  find  its  logical 
grounds  in  the  evidences  of  nature. 
1* 


lO  PROVINCE   OF  NATURAL  THEOLOGY. 

/      Here,    then,  is  the  first    great    office   of   natural 
/  theology.     It  furnishes  the  logical  basis  on  which 
I  the  whole  scheme  of  revealed  religion  given  us  in 
the  Bible  rests. 

I  have  no  desire  to  over-estimate  the  importance 
of  my  subject.     For  myself,  I  believe,  with  Paley, 
,  and  the  other  eminent  writers  of  the  same  class,  that 
\  the  fundamental  truths   of  our  religion  can  be  in- 
ferred from  the  constitution  of  the  human  mind  and 
\  from  the  course  of  nature  with  as  much  certainty  as 
'analogical  reasoning  can  ever  give.     But  still  I  know 
that  the  evidence  is  not  demonstrative  and  not  likely 
to  convince  the  sceptic ;  for  in  the  last  analysis  it 
rests  on  certain  assumptions  which  he  will  not  ad- 
mit.     And  it  is  in  vain  to  urge  that  these  assump- 
Itions  are  really  intuitive  truths  and  tacitly  admitted 
by  the  whole  human  race  ;  for  he  easily  replies,  that 
they  are  not  intuitive  to  his  mind. 
•     Nevertheless,  the  evidences  of  God  in  nature — in- 
cluding, of  course,  the  human   soul — are  the  only 
proof  we  have  or  can  have  of  his  existence,  and  they 
are,  therefore,  the  only  logical  basis  of  the  Christian 
revelation.     Nature  and  revelation  are  parts  of  one 
and  the  same  system,  and,  however  much  our  pre- 
judices may  obscure  the  fact,  Christianity  rests  on 
natural  religion,  and  cannot  be  logically  defended  if 
the  authority  of  the  last  is  denied. 

But  however  great  the  value  of  natural  theology, 
considered  as  the  basis  on  which  revelation  rests, 
this  is  not  its  only  or  most  important  office.  In  the 
present  age  of  the  world,  it  confers  a  still  more  ines- 
timable benefit  on  mankind  by  confirming,  illustrat- 


PROVINCE   OF  NATURAL  THEOLOGY.  II 

ing,  and  enforcing  the   admitted  truths  of   revela- 
tion. 
^       If  it  be  asked  of  what  value  are  further  illustra- 
\  tions  of  admitted  truths,  I  answer,  that  there  is  an 
j  important  class  of  nominal  Christians  who  are  more 
lopen  to  impressions  from  the  study  of  nature  than 
jto  direct  appeals  to  the  heart.     It  is  true  that  the 
great  mass  of  mankind  must  be  Christianized,  if  at 
all,  through  the  affections  and  by  the  hard  discipline 
of  sorrow ;  but  there  are  some  who,  not  yet  tried  in 
the  fiery  furnace  of  affliction,  have  first  felt  their 
Father's  hand   and  recognized  his  love  while  con- 
templating his  works.     I  do  not  say  that  persons  so 
touched  are  already  Christians,  but  I  do  say  that 
the  first  step  has  been  taken,  and  that  is  a  great  deal. 
It  may  require  many  years  of  sad  experience  and 
many  a  bitter  pang  of  disappointment  before  they 
come  to  kneel  humbly  at  their  Saviour's  feet ;  but, 
like  the  great  Apostle,  they  will  always  look  back 
to  the  time  when  the  Divine  presence  first  visibly 
shone  before  them  as  the  turning  period  of  their  life. 
While,  therefore,  I  should  be  the  first  to  condemn 
that  hollow    naturalism    which  would   substitute  a 
system  of  natural  theism  for  the  simple  doctrines 
of  the  Bible,  I  must  also  deprecate  that  prejudice 
which  prevents  many  clergymen,  through    fear  of 
this  tendency  of  the  age,  from  availing  themselves 
of  the  aid  of  science  in  enforcing  the  fundamental 
truths  of    our  religion.     I   assure  them    they  thus 
neglect  a  most  important  means  of  influence  over 
educated  and  thinking  men, — a  means  of  influence 
always  important,  but  never  more  so  than  in  an  age 


12  PROVINCE  OF  NATURAL  THEOLOGY. 

which  is  marked  by  its  cultivation  of  practical  sci- 
ence, and  in  a  country  where  so  large  a  portion  of 
the  active  energy  of  the  community  has  taken  this 
practical  direction.  The  danger  of  our  time  is  not 
so  much  a  philosophical  scepticism  as  a  practical 
materialism.  The  fear  is,  not  that  men  should 
reason  themselves  into  unbelief,  but  that,  spending 
their  whole  lives  in  developing  the  powers  of  nature, 
they  should  practically  worship  the  dead  matter 
rather  than  the  living  God.  If,  however,  we  can 
j  make  such  persons  feel  that  the  material  is  but  a 
form  of  the  spiritual,  and  that  in  fact  the  spiritual  is 
nowhere  more  manifest  than  in  those  very  laws  and 
forces  which  they  so  much  idolize,  we  shall  not 
change,  it  is  true,  the  tendency  of  the  age,  but  we 
shall  ennoble  and  sanctify  it.  The  whole  material 
universe  will  become  transfigured,  and  nature  will 
no  longer  be  seen  as  a  wonderful  mechanical  appli- 
cation of  blind  forces,  but  as  a  living  embodiment  of 
the  Eternal  One.  Nature-worship  may  continue,  but 
it  will  have  lost  its  idolatry  ;  for  it  will  be  no  longer 
the  machine  that  is  worshiped,  but  that  same  Liv- 
ing Spirit  which  spoke  in  tones  of  thundet*  from  the 
clouds  of  Sinai  and  in  accents  of  mercy  at  the  bap- 
tism of  Christ. 
r^  I  know  it  is  said  that  nature  conceals  rather  than 
(  reveals  God,  and  in  a  certain  sense  it  is  undoubtedly 
j  true  that  He  is  hidden  from  us  behind  the  veil  of  his 
I  works ;  but  since  it  is  permitted  to  man  by  the  exer- 
cise of  his  intelligence  to  Hft  in  part  this  veil,  it  is 
certainly  the  duty,  as  it  should  be  the  privilege,  of 
the  ministers   of   religion   to   show   forth   the   un- 


PROVINCE   OF  NATURAL  THEOLOGY.  1 3 

speakable  glory  which  lies  behind  these  material 
forms. 

But  why  multiply  arguments  when  we  have  the 
authority  of  the  Great  Teacher  himself,  who  fre- 
quently appealed  to  nature  to  illustrate  and  enforce 
the  divine  truths  which  he  came  on  earth  to  reveal  ? 
We  have  indeed  the  whole  summary  of  Natural 
Theology  in  His  simple  words : 

**  Wherefore,  if  God  so  clothe  the  grass  of  the 
field,  which  to-day  is,  and  to-morrow  is  cast  into 
the  oven,  shall  he  not  much  more  clothe  you,  O  ye 
of  little  faith?" 

With,  then,  such  authority  as  this,  let  us  not  de- 
spise the  beginnings  because  they  are  not  the  end, 
or  undervalue  the  means  by  which  many  a  noble 
soul  has  been  led  to  the  foot  of  the  Cross. 

Without  seeking,  therefore,  to  vindicate  further 
the  claims  of  my  subject,  I  will  at  once  enter  upon 
the  plan  already  proposed  for  this  course  of  lectures, 
and  will  first  ask  your  attention  to  the  illustrations  of 
the  wisdom,  goodness,  and  power  of  God,  which  may 
be  discovered  in  the  constitution  of  our  atmosphere. 
In  endeavoring  to  carry  out  this  plan,  I  shall  require 
all  your  indulgence  and  all  your  kind  forbearance. 
From  the  very  nature  of  the  case,  it  will  be  neces- 
sary to  start  from  first  principles,  and  much  of  the 
way  we  are  to  travel  together  will  be  uninteresting 
and  dull.  If,  however,  the  path  shall  lead  us  to  the 
summit  of  that  holy  mountain  from  which  we  can 
gain  a  clearer  vision  of  spiritual  things,  we  shall  soon 
forget  the  toil  and  difficulty  of  the  ascent.  We 
have   no    extravagant   expectations   of   the   result. 


14  ADAPTATIONS  TO   BE   STUDIED 

We  do  not  hope  to  convince  the  sceptic,  or  to  arouse 
the  indifferent  from  their  practical  unbelief.  Our 
only  hope  is — and  this  we  entertain  in  all  humility — 
that,  by  pointing  out  a  few  of  the  footprints  of  the 
Creator  which  lie  thickly  along  our  daily  path,  we 
may  encourage  some  earnest  student  toiling  forward 
on  his  journey  of  life.  May  God  grant  to  us  all  the 
richest  blessings  of  his  grace  ;  for  though  man  may 
plant  and  water.  He  only  giveth  the  increase. 

The  illustrations  of  the  attributes  of  God  pre- 
sented to  us  by  the  atmosphere  are  especiafly  mani- 
fest in  those  adaptations  of  properties  by  which  it 
has  been  made  to  subserve  the  welfare  and  happi- 
ness of  mankind,  and  this  is  to  be  expected,  not 
only  because  these  relations  have  been  the  most 
studied,  and  are,  therefore,  the  best  known,  but  also 
because  the  familiar  phenomena  through  which  our 
intelligences  are  connected  with  the  external  world, 
are  the  im.mediate  objects  of  our  observation  and 
cognizance.  Here,  however,  as  always  in  the  study 
of  nature,  we  must  be  careful  to  avoid  the  error 
of  considering  man  as  the  sole  end  of  creation,  and 
of  interpreting  all  phenomena  with  reference  to 
him  alone.  The  material  universe  is  the  manifes- 
tation of  one  grand  creative  thought,  as  compre- 
hensive in  the  diversity  of  the  parts  as  it  is  grand 
in  the  unity  of  the  whole.  These  parts  have 
been  so  wondrously  joined  and  skilfully  wrought 
together,  that  each  is  linked  with  each,  and  one 
with  all.  In  this  divine  economy  nothing  is  want- 
ing, nothing  is  superfluous,  and  what  seems  to  our 
feeble  vision  least  important  |s^  as_ess^^d|liaxom-- 

^     JL'ir  ^->  V^    .iv^^>^  (^  < 


'y^. 


WITH   REFERENCE  TO   MAN.  1 5 

p]ete  the  unity  of  the  plan  as  our  own  glorious  man- 
hood : 

"Nothing  useless  is  or  low, 

Each  thing  in  its  place  is  best, 
-  And  what  seems  but  idle  show 

.  /|.1  ^iLp  Strengthens  and  supports  the  rest." 

Amidst  all  this  wonderful  variety  in  unity,  man 
stands  the  culminating  glory  of  the  whole.  Made 
in  the  image  of  his  Creator,  and  but  "  a  little  lower 
than  the  angels,'*  he  has  been  intrusted  with  domin- 
ion and  power  over  all  the  brute  matter  which  sur- 
rounds him.  Through  the  long  ages  of  geological 
history  the  earth  was  preparing  for  his  dwelling,  and 
in  the  earliest  forms  of  animal  life  his  coming  was 
prefigured  and  foretold.     It  will  be  natural,  there- 


r, 


fore,  to^  consider  the  adaptations  of  the  atmosphere 
with  special  reference  to  him ;  and  this  we  may  do 
legitimately,  without  losing  sight  of  the  grand  idea 
which  underlies  the  whole,  and  of  which  man  is 
only  the  nobler  part. 

The  atmosphere  is  a  vast  ocean  of  aeriform  mat- 
ter, enveloping  the  earth  like  a  mantle,  and  rising  to 
the  height  of  many  miles  above  our  heads,  but  con- 
stantly diminishing  in  density  as  the  elevation  in- 
creases. At  the  height  of  about  three  miles  and  a 
half  (3.43)  the  density  is  only  one-half  as  great  as  at 
the  level  of  the  sea;  and  at  the  height  of  forty 
miles  it  is  less  than  in  the  exhausted  receiver  of  the 
best  air-pumps.  How  much  higher  than  this  the 
atmosphere  extends,  it  is  impossible  to  determine 
with  accuracy.  In  this  ocean  of  air  all  bodies  on  the 
surface  of  the  globe  are  immersed.     It  is  so  subtle 


l6  DESCRIPTION   OF  THE  ATMOSPHERE. 

that  it  penetrates  into  the  minute  pores  of  matter, 
and  fills  the  cavities  of  all  organized  being.  It  is 
the  medium  in  which  all  vital  processes  both  of 
plants  and  animals  take  place,  and  in  which  all 
human  activity  has  its  seat.  Let  us  see  now  with 
what  wisdom  its  properties  have  been  adapted  to 
the  important  ends  which  it  is  appointed  to  sub- 
serve. 

Consider,  in  the  first  place,  the  physical  state  of 
the  atmosphere,  its  very  aeriform  condition.  This 
air  is  as  truly  matter  as  the  solid  planks  on  which 
we  are  treading,  or  the  granite  rocks  on  which  this 
building  rests.  It  is  far  less  dense,  it  is  true,  but 
then  it  has  all  the  essential  properties  of  matter.  It 
fills  space.  It  resists  with  an  ever-increasing  force 
all  attempts  to  condense  it ;  and,  moreover,  it  has 
weight.  But  how  different  in  condition  from  the 
solid  rock ! — so  different  that  to  the  uneducated  it 
hardly  seems  material ;  and  in  our  common  language 
we  speak  of  a  space  which  is  filled  only  with  air  as 
empty.  Its  particles  are  endowed  with  such  perfect 
freedom  of  motion,  and  yield  so  readily  to  the 
slightest  pressure,  that  we  move  through  it  without 
feeling  its  presence.  It  is  firm  enough  to  support 
the  wings  of  the  lark  as  he  mounts  the  sky,  and  yet 
so  yielding  as  not  to  detain  the  tiniest  insect  in  its 
rapid  flight. 

The  physical  condition  of  the  atmosphere  will 
still  further  excite  our  admiration,  when  we  consider 
the  wonderful  play  of  forces  by  which  it  is  upheld. 
It  may  not  be  known  to  you  all  that  upon  this  mass 
of  air,  outwardly  so  calm  and  passive,  there  are  con- 


ITS  PHYSICAL  CONDITION.  1/ 

stantly  acting  two  mighty  forces, — the  force  of  grav- 
itation and  the  force  of  heat.  In  virtue  of  the 
force  of  heat  the  particles  of  the  atmosphere  mutu- 
ally repel  each  other,  and  the  whole  mass,  like  a 
bent  spring,  tends  to  break  from  its  confinement  and 
to  expand  into  the  surrounding  space  ;  but  this  it 
cannot  do,  for  by  the  power  of  gravitation  it  is  held 
with  a  firm  grasp  to  the  surface  of  the  globe.  Were 
this  grasp  for  a  moment  relaxed,  the  atmosphere 
would  dash  off  with  explosive  violence  and  be  lost 
in  the  immensity  which  surrounds  us.  How  great 
the  force  is  which  is  required  to  restrain  the  expan- 
sive tendency  of  the  atmosphere  few  persons  have 
an  adequate  conception,  because  the  two  opposing 
forces  are  so  perfectly  balanced  that  we  are  obliged 
to  call  in  the  aid  of  experiment  in  order  to  render 
their  effects  evident.  So  true  is  this,  that  the  world 
never  even  dreamed  of  their  existence  until  within 
two  hundred  years,  and  the  story  of  the  discovery  is 
one  of  the  most  remarkable  in  the  history  of  induc- 
tive philosophy.  This  story  is  well  known ;  but  as 
it  is  short,  and  teaches  us  an  important  truth,  you 
will  pardon  its  repetition. 

Every  one  who  has  seen  a  common  pump  is  fa- 
miliar with  the  fact  that  it  is  the  pressure  of  the  air 
which  causes  the  water  to  rise  in  the  suction-pipe, 
and  this  suction  is  one  manifestation  of  that  force 
by  which  the  atmosphere  is  held  so  firmly  to  the 
surface  of  the  globe.  The  pump,  however,  was  used 
long  before  the  discovery  of  the  pressure  of  the  at- 
mosphere, and  its  action  was  explained  by  a  prin- 
ciple which  seemed  perfectly  satisfactory  then,  but 


1 8        NATURE  ABHORS  A  VACUUM. 

which  sounds  strangely  enough  to  modern  ears. 
The  principle  appears  first  to  have  originated  with 
the  Aristotelians,  and  was  expressed  in  the  phrase, 
"  Nature  abhors  a  vacuum.'*  These  ancient  philos- 
ophers noticed  that  space  was  always  filled  with 
some  material  substance,  and  that  the  moment  a 
solid  body  was  removed  air  or  water  always  rushed 
in  to  fill  the  empty  space.  Hence  they  concluded 
that  it  was  a  universal  law  of  nature  that  space 
could  not  exist  unoccupied  by  matter,  and  the 
phrase  just  quoted  was  merely  their  figurative  ex- 
pression of  this  philosophical  idea.  When,  for  ex- 
ample, the  piston  of  a  common  pump  was  drawn  up, 
the  rise  of  the  water  was  explained  by  declaring, 
that,  as  from  the  nature  of  things  a  vacuum  could 
not  exist,  the  water  necessarily  filled  the  space  de- 
serted by  the  piston. 

This  physical  dogma  served  the  purpose  of  natural 
philosophy  for  two  thousand  years,  and  it  was  not 
until  the  seventeenth  century  that  men  discovered 
any  limit  to  nature's  abhorrence  of  a  vacuum.  Near 
the  middle  of  that  century  some  engineers  were 
employed  by  the  Duke  of  Tuscany  to  sink  a  well  in 
the  neighborhood  of  Florence  to  an  unusual  depth. 
They  finished  their  work,  but  on  adjusting  the  pump 
they  found  to  their  surprise  that  it  would  not  work. 
With  all  their  efforts  the  water  would  rise  only  a 
little  more  than  thirty  feet,  and  by  no  ingenuity  or 
skill  could  they  raise  it  an  inch  higher.  More  dis- 
gusted with  nature  than  nature  was  with  the  vacu- 
um in  their  pump,  they  applied  to  Galileo,  then  an 
old  man,  living  in  his  villa  on  the  brow  of  Fiesole. 


THE   PUMP-MAKERS  AND   GALILEO  1 9 

He  could  not  aid  them,  but  he  is  said  to  have  re- 
plied, half  in  jest,  half  in  earnest,  that  nature  did  not 
abhor  a  vacuum  above  thirty  feet.  Had  this  inci- 
dent occurred  earlier  in  his  career,  Galileo  would 
undoubtedly  have  added  to  the  other  jewels  of  his 
crown  a  brighter  gem  than  all,  but  now  the  vigor 
of  his  manhood  was  spent ;  he  had  done  his  work, 
and,  worn  out  by  the  persecution  M.  a  bigoted  priest- 
hood, he  was  peacefully  resting  from  his  life's  labor, 
and  calmly  awaiting  the  close. 

But  the  key  which  the  incident  had  furnished  was 
not  lost.  It  passed  into  able  hands,  and  it  was  the 
fortune  of  Torricelli,  Galileo's  best  pupil,  to  unlock 
the  secret.  This  young  Italian  philosopher,  whose 
clear,  intellect  had  been  trained  in  the  mechanical 
philosophy  of  his  great  master,  saw  at  once  that  a 
column  of  water  thirty-three  feet  high,  and  no  higher, 
could  not  be  sustained  in  a  cylindrical  tube  by  a 
mere  metaphysical  abstraction. 

This  effect,  he  said,  must  be  the  result  of  some 
mechanical  force  equivalent  to  the  weight  of  the 
mass  of  water  sustained.  It  was  not  difficult  to 
prove  the  correctness  of  this  reasoning,  for  it  was 
evident  that  if  a  column  of  water  was  sustained  at 
the  height  of  thirty-three  feet  in  the  suction-pipe  of  a 
pump  by  a  constant  force,  the  same  force  could  only 
sustain  a  column  of  a  heavier  liquid  at  a  proportion- 
ally less  height.  So  Torricelli  tried  mercury,  a 
liquid  thirteen  and  a  half  times  heavier  than  water, 
and  the  result  was  as  he  had  anticipated.  The  force 
which  raised  the  column  of  water  thirty-three  feet 
could  only  raise  a  column  of  mercury  to  the  height 


20  EXPERIMENT   OF  TORRICELLI. 

of  thirty  inches,  which  is  thirteen  and  a  half  times 
less  than  thirty-three  feet.  Torricelli  did  not,  how- 
ever, make  this  experiment  with  a  pump,  but  with 
an  apparatus  of  his  own,  much  simpler,  and  equally 
effective. 

He  took  a  long  glass  tube,  open  at  one  end,  filled 
it  with  mercury,  and,  having  closed  the  opening  with 
his  thumb,  inverted  the  tube,  and  plunged  the  open 
end  in  a  basin  of  mercury ;  on  removing  his  thumb, 
the  mercury,  instead  of  remaining  in  the  tube,  and 
thus  satisfying  nature's  abhorrence  of  a  vacuum,  fell, 
as  he  expected,  and,  after  a  few  oscillations,  came 
to  rest  at  a  height  of  about  thirty  inches  above  the 
level  of  the  mercury  in  the  basin.  The  correctness 
of  his  induction  having  been  thus  verified,  Torricelli 
at  once  concluded  that  it  must  be  the  pressure  of  the 
air  which  sustained  both  the  water  in  the  pump  and 
the  mercury  in  his  tube. 

This  experiment  excited  a  great  sensation  in  Eu- 
rope ;  but,  as  might  naturally  have  been  expected, 
the  old  physical  dogma  was  not  easily  laid  aside, 
and  Torricelli  did  not  live  to  see  his  opinion  gener- 
ally received.  It  was  left  to  the  celebrated  Blaise 
Pascal  to  convince  the  world  that  Torricelli  was 
right,  and  this  he  did  by  one  of  those  master-strokes 
of  genius  which  at  once  silence  controversy. 

"  If,'*  said  Pascal,  "  it  be  really  the  weight  of  the 
atmosphere  under  which  we  live  that  supports  the 
column  of  mercury  in  Torricelli's  tube,  we  shall  find, 
by  transporting  this  tube  upward  in  the  atmos- 
phere, that  in  proportion  as  it  leaves  below  it  more 
and  more  of  the  air,  and  has  consequently  less  and 


DEMONSTRATION   OF  PASCAL.  21 

less  above  it,  there  will  be  a  less  column  sustained 
in  the  tube,  inasmuch  as  the  weight  of  the  air  above 
the  tube,  which  is  declared  by  Torricelli  to  be  the 
force  which  sustains  it,  will  be  diminished  by  the  in- 
creased elevation  of  the  tube." 

Accordingly  Pascal  carried  the  tube  to  the  top  of 
a  church-steeple  in  Paris,  and  observed  that  the 
mercury  fell  slightly ;  but  not  satisfied  with  this  re- 
sult, he  wrote  to  his  brother-in-law,  who  lived  near 
the  high  mountain  of  Puy  de  Dome,  in  Auvergne, 
to  make  the  experiment  there,  where  the  result 
would  be  more  decisive. 

'*  You  see,"  he  writes,  "that  if  it  happens  that  the 
height  of  the  mercury  at  the  top  of  the  hill  be  less 
than  at  the  bottom  (which  I  have  many  reasons  to 
believe,  though  all  those  who  have  thought  about  it 
are  of  a  different  opinion),  it  will  follow  that  the 
weight  and  pressure  of  the  air  are  the  sole  cause  of 
this  suspension,  and  not  the  horror  of  a  vacuum ; 
since  it  is  very  certain  that  there  is  more  air  to 
weigh  on  it  at  the  bottom  than  at  the  top ;  while 
we  cannot  say  that  nature  abhors  a  vacuum  at  the 
foot  of  a  mountain  more  than  on  its  summit."  M. 
Perrier,  Pascal's  correspondent,  made  the  observa- 
tion as  he  desired,  and  found  a  difference  of  about 
three  inches,  "which,"  as  he  replies,  "ravished  us 
with  admiration  and  astonishment." 

Thus  it  was  that  man  first  learned  to  recognize 
the  existence  of  that  power,  which  retains  the  at- 
mosphere on  the  surface  of  the  globe,  and  the  his- 
tory of  the  discovery  should  humble  our  intellectual 
pride  and  teach  us  to  hold  our  knowledge  with  rev- 


22  THE   OLD   DOGMA 

erence  and  humility.  This  old  scientific  dogma  of 
the  seventeenth  century  never  fails  to  excite  a 
smile,  and  we  are  inclined  to  wonder  how  man  could 
ever  have  believed  what  now  appears  so  absurd  ; 
but  if,  like  an  antiquary,  we  imbue  our  minds  with 
the  spirit  of  that  age,  it  will  be  seen,  not  only  that 
the  dogma  was  not  essentially  absurd,  but  also  that 
the  philosophical  idea,^clothed  in  those  quaint 
terms,  appeared  to  the  scientific  men  of  the  period 
as  truly  a  legitimate  induction  from  observed  facts 
as  the  law  of  gravitation  seems  to  us.  And  the  in- 
duction was  legitimate  ;  but  since  the  known  facts 
did  not  cover  the  whole  ground,  they  gave  only  a 
very  partial  truth.  The  Grand  Duke's  pump  was  the 
first  failing  case,  and  proved,  not  that  the  old  prin- 
ciple was  absolutely  false,  but  only  that  its  applica- 
tion was  very  limited. 

Thanks  to  Galileo,  Torricelli,  Pascal,  and  New- 
ton— noble  line  of  genius — nature's  abhorrence  of  a 
vacuum  gave  place  to  the  law  of  gravitation,  and 
two  centuries  of  unparalleled  scientific  activity  have 
only  served  to  confirm  the  truth,  and  extend  the 
domain  of  Newton's  grand  generalization ;  but  even 
after  this  signal  triumph,  who  now  feels  fully  assured 
that  the  law  of  gravitation  may  not  find  its  failing 
case?  and  when,  two  centuries  hence,  the  future 
historian  comes  to  write  the  history  of  inductive 
philosophy,  who  can  feel  certain  that  Aristotle's 
dogma  and  Newton's  law  may  not  both  be  conde- 
scendingly noticed  among  the  partial  truths  which 
served  the  purposes  of  science  in  its  infancy  and 
childhood  ? 


A   PARTIAL  TRUTH.  23 

Let  me  not  be  understood  to  imply  a  belief  that 
man  cannot  attain  to  any  absolute  scientific  truth, 
for  I  believe  that  he  can,  "a^nSTl  feel  that  every 
great  generalization  brings  him  a  step  nearer  to  the 
promised  goal ;  but  I  wish  here  at  the  outset  most 
strongly  to  impress  the  distinction  between  the  un- 
doubted facts  of  science,  and  the  laws  and  princi- 
ples which  have  grown  up  around  them,  and  by 
which  they  have  been  embodied  in  our  systems  of 
philosophy, — the  distinction,  in  a  word,  between  the 
observed  phenomena  of  nature,  and  man*s  interpre- 
tation of  the  phenomena. 

This  distinction,  so  obvious  when  stated,  is  too 
often  forgotten,  and  is  necessarily  overlooked  in  our 
scientific  text-books.  It  is  the  sole  aim  of  these 
elementary  treatises  to  teach  the  present  state  of 
knowledge,  and  they  would  fail  in  their  object  if 
they  attempted  by  a  critical  analysis  to  separate  the 
phenomena  from  the  laws  or  systems  by  which  alone 
the  facts  of  nature  are  correlated  and  rendered  in- 
telligible. But  although  while  studying  science  it- 
self, we  may  for  the  time  waive  the  distinction  be- 
tween fact  and  theory,  the  moment  we  come  to  com- 
pare the  results  of  science  with  the  eternal  verities 
of  religion,  the  distinction  here  enforced  becomes  of 
paramount  importance,  and  it  must  be  our  chief  aim 
to  separate  that  which  is  absolute  and  eternal  truth 
from  that  which,  even  in  its  highest  development,  is 
the  result  of  human  thought,  and,  like  all  things 
human,  subject  to  limitations  and  liable  to  change. 

Had  this  distinction  been  always  borne  in  mind, 
the  controversies  between  the  philosophers  and  the 


24  FACT  AND   THEORY. 

churchmen  would  have  been  less  bitter  and  more 
fruitful  in  truth  ;  the  philosophers  would  have  been 
willing  to  waive  their  theories,  and  the  churchmen 
would  have  been  led  to  respect  the  results  of  sci- 
ence, and  conform  their  theology  to  the  indisputable 
truths  which  God  has  been  pleased  to  reveal  through 
nature  no  less  plainly  than  in  his  written  word ;  and 
if  the  trite  anecdote  of  Galileo  and  the  pump- 
makers  serve  to  impress  the  distinction  on  our 
minds,  this  digression  will  not  have  been  made  in 
vain. 

You  must  all  have  recognized  in  Torricelli's  tube 
our  modern  barometer.  By  means  of  this  well- 
known  instrument  we  can  readily  estimate  the  press- 
ure of  the  atmosphere,  and  determine  the  amount 
in  our  human  standards  of  measurement.  It  can  be 
readily  proved  that  the  pressure  of  the  atmosphere 
is  about  fifteen  pounds  on  every  square  inch  of  the 
earth^s  surface,  and  if,  starting  from  this  well-known 
fact,  you  calculate  the  amount  of  pressure  on  any 
extended  surface,  you  will  be  astonished  at  the  re- 
sult. For  example,  the  pressure  exerted  by  the  at- 
mosphere on  the  area  on  which  this  building  stands 
is  much  greater  than  the  whole  weight  of  the  build- 
ing itself.  The  pressure  on  a  man  of  ordinary  stat- 
ure is  about  sixteen  tons ;  that  on  one  square  mile 
of  surface  is  equal  to  over  twenty-six  million  tons. 

How  great,  then,  must  be  the  pressure  on  the 
whole  surface  of  the  globe,  or,  what  is  the  same 
thing,  how  great  is  the  intensity  of  that  ever-acting 
power,  which  holds  the  atmosphere  in  its  appointed 
place !     It  would  not  be  difficult  to  calculate  the 


PRESSURE   OF  THE  ATMOSPHERE.  2$ 

amount  and  to  express  it  in  numbers;  but  these 
numbers  would  convey  to  you  no  definite  idea,  for 
our  minds  are  incapable  of  forming  an  adequate  con- 
ception of  such  immensity.  The  attempt  to  grasp 
it  only  exposes  our  weakness,  and  yet  this  force, 
immense  as  it  is,  is  so  delicately  balanced  by  the 
sweet  influences  of  the  sunbeam,  that  it  does  not  so 
much  as  shake  the  aspen-leaf  or  break  the  gossa- 
mer. If  we  believe  no  more  than  this,  that  the 
world  was  once  created  by  God,  what  must  be  the 
power  and  wisdom  of  a  being  who  could  appoint 
these  mighty  forces  and  adjust  them  with  such  per- 
fect precision !  .  But  if  we  also  believe  that  these 
forces  are  direct  emanations  of  Divine  Power, — that 
it  is  God  himself  who  with  his  own  right  hand  holds 
the  atmosphere  in  its  place,  and  appoints  its 
bounds, — then  all  nature  assumes  a  more  glorious 
aspect,  and  we  feel  that  we  are  indeed  surrounded 
by  the  Divine  Presence.  Yet  this  force,  which  we 
find  so  far  beyond  our  powers  of  conception,  is  but 
a  secondary  phase  of  that  immeasurably  greater 
power  which  brings  forth  Mazzaroth  in  his  sea- 
son, and  guides  Arcturus  with  his  sons.  How  fu- 
tile all  attempts  to  measure  Divine  power !  We 
select  some  one  of  the  feeble  forces  acting  around 
us,  and  succeed  in  reducing  its  value  to  our  human 
standards  of  comparison,  and  expressing  this  value 
in  numbers  ;  but  the  numbers,  when  obtained,  are 
beyond  our  grasp,  and  we  find  that  we  have  merely 
mounted  to  a  little  higher  platform,  from  which  we 
discover  numberless  other  forces  immeasurably 
greater  than  the  first.  Something,  however,  has 
3 


26  IDEA  OF  THE   INFINITE. 

been  gained.  We  have  attained  to  the  idea  of  the 
infinite  ;  and  to  thoroughly  apprehend  the  existence 
of  the  infinite,  is  to  take  the  first  step  toward  recog- 
nizing the  existence  of  a  God. 

I  know  it  will  be  said  that  man  cannot  compre- 
hend the  infinite,  and  if  by  this  statement  it  is  only 
meant  to  affirm  the  declaration  of  the  Bible,  that 
man  cannot  "find  out  the  Almighty  unto  perfec- 
tion," not  even  the  most  visionary  dreamer  would 
question  the  position.  But  there  is  a  class  of 
philosophers  at  the  present  day  who  think  to  enforce 
the  authority  of  revelation  by  maintaining  the  doc- 
trine that  man  can  know  absolutely  nothing  of  the 
infinite, — nothing  more  than  he  now  knows  of  the 
facts  or  principles  of  science  to  be  hereafter  discov- 
ered ;  that,  indeed,  the  very  term  infinite  implies  a 
negation  of  all  cognizable  qualities. 

To  me,  this  position  seems  fatal  to.  the  very  cause 
it  is  intended  to  defend,  and  surrenders  all  the  ap- 
proaches of  the  citadel  to  the  infidel.  For  if  there 
is  in  man  no  possibility  of  apprehending  the  infinite, 
even  to  the  smallest  degree,  I  can  see  nothing  to 
which  revelation  can  appeal.  He  has  then  no  power 
to  distinguish  between  the  Divine  and  the  human. 

But  it  is  riot  so.  Revelation  implies,  and  all  ex- 
perience shows,  that  man  can  recognize  the  pres- 
ence of  the  infinite  by  attributes  as  clear  and  unmis-' 
takable  as  those  which  mark  the  presence  of  the 
finite  matter  around  him.  He  may  not  be  able  to 
comprehend  a  single  attribute  of  the  infinite  in  its 
essence;  but  as  the  mathematician,  dealing  with 
infinitesimal  quantities,  which  he  cannot  fully  un- 


IDEA   OF  THE   INFINITE.  2/ 

derstand,  arrives  at  truths  of  the  material  world 
with  all  the  certainty  of  demonstration,  so  the  men- 
tal philosopher  may  attain  to  moral  truths  in  regard 
to  the  Infinite  Being,  although  the  very  terms  he 
employs  may  be  veiled  in  impenetrable  mystery. 

And  what  is  the  true  human  conception  of  the 
infinite?  It  is  not  merely  something  which  we  feel 
to  be  very  great  indeed,  but  it  is  something  which 
we  feel  surpasses  our  utmost  conceptions  of  the 
great, — something  which,  let  us  account  it  as  great 
as  we  please,  yet,  wherever  the  inability  of  our 
mental  power  fixes  the  limit  of  our  conception,  will 
still  be  felt  to  be  greater  than  the  greatest.  We 
cannot  gaze  into  the  heavens  without  awe  ;  we  can- 
not examine  the  wonders  of  the  dew-drop  without 
reverence  ;  we  cannot  look  into  our  own  souls 
without  trembling.  It  is  the  same  invisible  Pres- 
ence everywhere,  and  however  long  false  philosophy  > 
may  conceal  the  vision,  or  material  cares  and  pleas-  :^  ^ 
ures  blind  the  senses,  when  man  once  recognizes  o^^  ^^^ 
its  existence  he  instinctively  worships  and  adores.            ^^ 

The  far-reaching  relations  of  the  adaptations  we  '^ 
are  now  studying  become  evident  when  we  con- 
sider that  the  density  of  the  atmosphere  is  one  of 
the  conditions  of  organic  life  on  the  surface  of  the 
globe.  By  density  is  meant,  I  need  not  state,  the 
quantity  of  matter  which  the  atmosphere  contains 
in  a  given  volume  ;  for  example,  in  a  cubic  yard. 
This  quantity  is  capable  of  exact  measurement,  and 
although  to  a  certain  extent  variable,  it  is  constant 
in  the  same  place,  under  the  same  conditions  of 
temperature  and  pressure. 


o 


28  DENSITY   OF  THE  ATMOSPHERE. 

In  this  latitude,  at  the  level  of  the  sea,  one  cubic 
yard  of  the  atmosphere,  when  dry  and  under  the  . 
normal  conditions  of  temperature  and  pressure,  con- 
tains about  two  pounds  of  air,  and  this  weight  is  the 
measure  of  its  density.  Now  we  find  that  the  or- 
garkization  of  plants  and  animals,  including  man,  has 
been  adjusted  to  the  density  of  the  air,  and  illus- 
trations of  this  adaptation  will  be  met  with  as  we 
proceed.  But  accepting  the  fact  for  the  present  as 
universally  conceded,  let  us  consider  the  conditions 
on  which  this  adaptation  of  the  air  to  our  physical 
organization  rests. 

The  density  of  the  atmosphere  may  be  said  to  de- 
pend upon  four  conditions  :  first,  on  the  inherent 
nature  of  the  substance  which  we  call  air  itself;  sec- 
ondly, on  the  intensity  of  gravity ;  thirdly,  on  the 
total  quantity  of  air  on  the  globe ;  and,  lastly,  on 
the  temperature.  The  influence  of  the  first  condi- 
tion is  not  understood,  but  that  of  the  last  three  we 
can  readily  trace.  If  the  intensity  of  the  force  of 
gravity  at  the  surface  of  the  earth  were  to  change, 
other  circumstances  remaining  the  same,  the  density 
of  the  atmosphere  would  change  in  the  same  pro- 
portion. Thus,  for  example,  if  the  intensity  of 
gravity  on  the  earth  were  as  great  as  it  is  on  the 
surface  of  the  sun,  the  density  of  the  atmosphere 
would  be  twenty-eight  times  as  great  as  at  present ; 
or  if  this  intensity  were  reduced  to  that  which  exists 
on  the  surface  of  the  moon,  the  density  would  be 
diminished  to  one-sixth  of  the  existing  density. 

But,  assuming  that  the  intensity  of  the  force  of 
gravity  on  the  surface  of  the  earth  remained  con- 


DENSITY   OF  THE  ATMOSPHERE.  29 

stant,  precisely  the  same  effect  would  result  from 
any  variation  in  the  total  quantity  of  the  atmos- 
phere. Were  the  whole  amount  of  air  on  the  earth 
increased  or  diminished,  the  density  of  the  atmos- 
phere at  its  surface  would  also  be  increased  or  di- 
minished in  the  same  proportion.  Still  further,  as- 
suming that,  while  the  intensity  of  gravity  and  the 
mass  of  the  atmosphere  remained  fixed,  the  tem- 
perature were  changed,  then  also  the  density  of  the 
atmosphere  would  vary,  and  by  a  quantity  which 
can  be  easily  determined.  By  accurate  experiments 
it  has  been  ascertained  that  an  elevation  of  tem- 
perature equivalent  to  about  five  hundred  degrees 
of  our  Fahrenheit  thermometer  would  reduce  the 
density  to  one-half ;  and,  on  the  other  hand,  that  a 
reduction  of  temperature  would  increase  the  density 
in  the  same  proportion. 

Consider  next  what  these  relations  imply.  Re- 
flect that  the  intensity  of  the  force  of  gravity  de- 
pends upon  the  mass  of  the  earth.  Remember  that 
the  mean  temperature  depends  upon  the  distance 
of  the  earth  from  the  sun,  and  you  will  see  that  not 
only  the  actual  size  of  the  earth,  but  also  its  dis- 
tance from  the  sun,  and  the  quantity  of  air  on  its 
surface,  were  all  necessary  conditions  in  order  that 
the  atmosphere  should  have  its  present  density,  and 
thus  become  the  fit  abode  for  the  actual  families  of 
organic  beings.  If  any  one  of  these  conditions  had 
been  different,  the  same  result  would  not  have  been 
attained,  and  man,  as  he  exists,  could  not  have  lived 
on  this  globe. 

It  must  then  have  been  He  **  who  hath  meted  out 

\ 


30  UNITY   OF  THE  DESIGN. 

heaven  with  the  span,  and  comprehended  the  dust  of 
the  earth  in  a  measure,  and  weighed  the  mountains 
in  scales,  and  the  hills  in  a  balance,"  who  "  formed 
man  of  the  dust  of  the  ground,  and  breathed  into 
his  nostrils  the  breath  of  life." 

The  unity  of  the  design  implies  the  oneness  of 
the  designer,  and  although  the  adaptations  just  con- 
sidered may  not  exclude  every  possible  atheistic 
theory  of  cosmogony,  yet  they  show  conclusively 
that,  if  there  is  design  anywhere,  there  is  design 
everywhere ;  if  there  is  design  in  the  least,  there  is 
design  also  in  the  greatest,  and  design  in  the  atom 
may  thus  confirm  the  evidence  of  design  in  man. 


f  L 1  R  11  A  I ;  \ 

tJNIVKHHITV   OF 

CALlFOilXIA. 


CHAPTER   II. 

TESTIMONY  OF  THE  ATMOSPHERE. — Concluded. 

During  a  recent  journey  in  Switzerland,  at  the 
close  of  a  delightful  summer's  day,  in  the  early  part 
of  July,  I  arrived  at  Interlachen,  in  company  with 
a  number  of  fellow-travellers.  We  had  been  saiHng 
on  the  beautiful  lake  of  Brienz,  and  some  minutes 
before  we  reached  our  destination  the  sun  had  set, 
and  the  mountains  had  already  cast  their  long  shad- 
ows across  the  lake.  Early  in  the  kfternoon  the 
clouds  had  settled  on  the  nearer  hills,  and  we  had 
been  disappointed  at  not  obtaining  a  view  of  the 
distant  summits  of  the  Bernese  Oberland  ;  but  sud- 
denly, as  the  boat  neared  the  shore,  the  magnificent 
peak  of  the  Jungfrau  appeared  from  behind  the  veil 
of  clouds,  clothed  in  her  white  mantle  of  everlasting 
snow,  and  bathed  with  a  flood  of  rosy  light.  The 
effect  thus  heightened  by  the  contrast  was  grand 
beyond  description,  and  as  beautiful  as  it  was 
grand.  It  seemed  like  a  vision  of  the  Heavenly 
Kingdom, — as  if  the  glory  of  God  had  rested  on  the 
mountain.  The  scene  completely  filled  the  soul, 
and  the  heart  overflowed  with  gratitude  for  the 
blessing  it  enjoyed.     It  was  felt  to  be  one  of  the 

31 


32  THE  ATMOSPHERE  AND   LIGHT. 

great  privileges  of  a  lifetime,  and  his  would  have 
been  a  dull  understanding,  and  a  duller  heart,  which 
did  not  recognize  the  Giver  in  the  gift.  The  view 
so  riveted  the  attention  that  we  hardly  noticed  our 
arrival,  and  as  we  walked  to  the  hotel  we  watched 
the  successive  shades  of  crimson  and  purple  as  they 
flitted  up  the  mountain,  until  the  last  blended  in 
the  gray  of  the  twilight. 

It  may  not  be  permitted  to  many  to  behold  the 
Jungfrau  blushing  before  her  retiring  lord,  but  all 
have  witnessed  the  same  effect  on  even  a  grander 
scale,  when  the  white  clouds,  piled  up  on  the  west- 
ern horizon  like  vast  mountain  chains,  become,  at 
evening,  resplendent  with  the  rays  of  the  setting 
sun  ;  and  many  have  watched  their  varying  tints  of 
gold  and  purple,  until  at  last  their  ghostly  forms 
vanished  in  the  dusk  of  the  evening,  and  the  stars 
came  out  to  take  up  with  their  measured  twinkling 
the  silent  song  of  praise.  Perhaps,  also,  there  may 
be  some  who,  after  anxious  watching  through  the 
night,  have  felt  their  hearts  strengthened  and  their 
hopes  revived  when  the  blush  of  morning  reassured 
them  of  their  Father's  providence,  and  all  nature 
smiled  in  the  floods  of  returning  light. 

All  these  glorious  visions,  all  this  beauty,  and  all 
the  pure  emotions  of  our  hearts  which  they  excite, 
we  owe,  my  friends,  to  the  skill  with  which  the 
physical  qualities  of  the  atmosphere  have  been  ad- 
justed to  the  wants  of  our  physical  and  moral  na- 
tures, and  they  all  thus  become  the  silent  witnesses 
not  only  of  the  wisdom,  but  also  of  the  goodness  of 
our  God. 


TRANSPARENCY.  33 


We  have  already,  in  the  first  lecture,  discussed 
some  of  the  adaptations  of  the  physical  condition  of 
the  atmosphere  to  the  purposes  which  it  subserves 
on  the  globe,  and  I  wish  this  evening  to  develop 
still  further  the  same  subject,  by  considering  a  few 
additional  examples ;  and  first  I  will  ask  your  atten- 
tion to  those  evidences  of  design  which  are  to  be 
found  in  the  f-elations  of  the  atmosphere  to  light  and 
heat.  Here,  however,  I  am  met  by  a  difficulty.  In 
order  to  explain  fully  these  relations  it  would  be 
necessary  to  develop  from  first  principles  the  sci- 
ences of  optics  and  thermotics,  and  to  do  this  in  a 
popular  manner  would  require  several  lectures. 
These  sciences  furnish  some  of  the  most  wonderful 
evidences  of  design  which  are  to  be  found  in  nature, 
and  I  have  no  doubt  will  be  given  their  appropriate 
place  in  this  series  of  lectures.  Without,  therefore, 
attempting  any  detailed  explanations,  I  will  merely 
bring  before  you  a  few  facts,  drawn  from  these  de- 
partments of  knowledge,  which  illustrate  the  adapta- 
tions of  the  atmosphere  to  its  appointed  ends. 

The  atmosphere,  although  very  much  more  per- 
vious to  light  than  any  kind  of  solid  or  liquid  mat- 
ter, is  far  from  being  perfectly  transparent.  Indeed, 
the  reverse  is  sufficiently  evident  from  our  daily  ex- 
perience. Every  one  has  noticed  that  distant  ob- 
jects appear  less  distinct  in  proportion  as  they  are 
removed,  their  colors  become  fainter,  the  contrast 
between  light  and  shade  less  marked,  and  that  they 
seem  as  if  covered  with  a  pale  blue  veil.  This  effect, 
always  noticed  on  distant  mountains,  is  owing  to  a 
partial  absorption  of  the  light  while  passing  through 
2* 


34  DIFFUSION   OF   LIGHT. 

the  atmosphere ;  for,  were  the  passage  of  the  rays 
wholly  unimpeded,  all  objects,  although  reduced  in 
size  in  proportion  to  their  distance,  would  appear 
equally  distinct,  and  their  colors  equally  brilliant. 

The  transparency  of  the  atmosphere  differs  very 
greatly  under  different  circumstances,  but  it  has 
been  estimated  that,  under  the  most  favorable  con- 
ditions, at  least  thirty  per  cent,  of  all  the  light  com- 
ing from  the  heavenly  bodies  is  absorbed  before 
reaching  the  surface  of  the  earth,  and  in  our  latitude, 
at  this  season,  even  when  the  sun  is  on  the  meridian 
and  the  sky  clear,  fully  one-half  of  his  rays  are  thus 
spent.  Do  not  suppose,  however,  that  all  the  light 
so  expended  is  lost.  Quite  the  contrary,  for  every 
particle  of  the  atmosphere,  illuminated  by  the  sun- 
beam, becomes  itself  a  new  centre  of  emission,  radi- 
ating the  light  in  every  direction. 

This  diffusion  of  the  sun's  rays  is  the  cause  of  that 
wonderful  effect  which  we  term  daylight.  I  say 
wonderful  effect,  for,  although  so  familiar,  it  is  one 
of  the  most  remarkable  results  of  skilful  adaptation 
and  infinite  wisdom.  The  very  daylight  which 
streams  in  at  the  open  windows  of  our  houses,  filling 
them  with  cheerfulness,  and  penetrating  to  their  in- 
most recesses,  which  enlivens  the  whole  landscape, 
and  which  bars  and  bolts  cannot  wholly  exclude 
even  from  the  prisoner's  dungeon,  is  another  evi- 
dence of  the  adaptation  of  the  atmosphere  to  the 
constitution  of  man.  Indeed,  the  atmosphere  is  as 
much  an  essential  condition  of  our  seeing  as  of  our 
breathing,  and  the  immeasurable  pleasure  which  we 
derive  from  our  sense  of  vision  depends  upon  its 


DIFFUSION   OF   LIGHT.  35 

adaptation  to  the  organization  of  the  eye.  Were  it 
not  for  the  diffusive  effect  of  the  atmosphere  on  the 
sun's  Hght,  the  contrast  between  light  and  shadows 
would  be  so  greatly  increased  that,  while  objects  di- 
rectly illuminated  by  the  sun  would  shine  so  brill- 
iantly as  to  dazzle  the  eyes,  all  surrounding  objects 
would  be  in  darkness,  and  the  interior  of  our  dwell- 
ings would  be  as  dark  as  night.  Our  eyes,  as  little 
fitted  to  such  conditions  as  our  lungs,  would  be 
blinded  by  the  sudden  alternations,  and  distinct  vision 
would  be  impossible.  This  is  not  a  matter  of  theory, 
for  similar  effects  are  observed  on  the  summits  of 
lofty  mountains,  where  the  air  is  much  rarer  than  at 
the  sea  level.  On  the  top  of  Mont  Blanc  the  sky 
has  a  blackish  hue,  and  the  stars  are  seen  at  midday; 
the  glare  of  the  direct  light  is  insupportable  to  the 
eye,  and  even  the  reflection  from  the  snow  blisters 
the  unprotected  skin,  while  at  the  same  time  the 
contrast  between  light  and  shade,  unnaturally  in- 
creased, gives  to  all  near  objects  a  peculiar  and 
ghastly  aspect.  We  have  here,  it  is  true,  a  very 
great  diminution  in  the  density  of  the  air ;  but  when 
you  reflect  upon  what  delicate  contrasts  of  light  and 
shade  the  beauty  of  a  landscape  depends, — the 
clearness  of  the  foreground,  the  gray  of  the  middle 
distance,  and  the  tender  purple  of  the  distant  hills 
all  blending  into  one  harmonious  whole, — you  can 
appreciate  how  slight  a  change  would  disturb  the 
result,  and  deprive  the  sense  of  beauty  of  its  purest 
enjoyment. 

I  have  thus  far  spoken  only  of  the  influence  of  the 
atmosphere  in  softening  the  intensity  of  the  rays  of 


36  COLOR  OF  THE  SKY. 

light,  and  in  diffusing  their  action ;  but  the  atmos- 
phere has  also,  under  certain  conditions,  the  power 
of  decomposing  the  sun's  rays,  and  thus  producing, 
not  only  those  displays  of  gorgeous  tints  which  we 
witness  in  the  sunset  clouds,  but  also  the  pure  blue 
which  colors  the  dome  of  heaven. 

In  regard  to  the  precise  means  which  are  em- 
ployed by  nature  to  produce  these  results,  scientific 
men  are  not  agreed.  It  has  been  proved  that  the 
blue  color  of  the  sky  is  seen  by  reflected  light,  and 
it  is  probable  that  the  color  is  caused  by  repeated 
reflections  of  the  sun's  rays  from  the  surfaces  of  the 
innumerable  small  water-bubbles  which  are  con- 
stantly floating  in  the  atmosphere.  You  have  all 
noticed  the  blue  color  of  the  soap-bubble  shortly 
before  it  breaks.  This  color  is  caused  by  the  action 
of  the  very  thin  film  of  water  in  decomposing  the 
light  reflected  from  its  surface,  and  it  is  supposed  to 
be  an  action  of  the  same  sort,  only  very  much  in- 
creased by  repeated  reflections,  which  gives  to  the 
sky  its  azure  hue. 

While  the  blue  color  of  the  sky  appears  to  result 
from  changes  in  the  white  light  of  the  sun  caused  by 
reflection,  it  is  equally  probable  that  the  sunset  tints 
arise  from  changes  in  the  same  white  light  caused 
by  an  unequal  absorption  of  its  different  colored 
rays  during  their  transmission  through  the  atmos- 
phere. Here,  again,  the  vapor  in  the  air  is  sup- 
posed to  be  the  active  agent ;  and  the  theory  is, 
that  the  tints  are  produced  while  the  vapor  is  con- 
densing into  clouds, — a  change  which  naturally 
occurs  at  sunset.     But  this  is  a  mere  theory,  and 


SUNSET  TINTS.  3/ 


our  whole  knowledge  on  these  subjects  is  very  im- 
perfect. 

So  far,  however,  as  our  present  argument  is  con- 
cerned, it  is  not  essential  that  we  should  understand 
exactly  how  these  glorious  results  are  obtained. 
It  is  enough  that  we  are  constantly  enjoying  their 
beauty,  and  that  we  know  they  are  owing  to  the 
peculiar  constitution  of  the  atmosphere.  When  fu- 
ture discoveries  shall  bring  to  light  the  methods, 
at  present  secret,  by  which  nature  gilds  the  sunset 
clouds  and  covers  our  beautiful  dwelling-place  with 
its  canopy  of  blue,  we  shall  unquestionably  find 
fresh  evidences  of  God's  wisdom  ;  but  even  now, 
when  ignorant,  perhaps,  of  these  hidden  causes, 
we  have  that  which  is  far  more  excellent,  the 
most  conclusive  evidence  of  His  goodness  and  love. 
Our  Father  has  not  only  adapted  the  atmosphere 
to  the  wants  of  our  bodies,  and  made  it  condu- 
cive to  our  physical  enjoyment,  but  He  has  also  made 
it  the  scene  of  the  highest  beauty, — a  beauty  which 
satisfies  the  longings  of  our  souls  and  calls  forth 
their  noblest  and  purest  aspirations.  Man,  sinful 
as  he  is,  cannot  look  up  into  the  pure  blue  of 
heaven  without  a  sense  of  reproach,  and  the  feeling 
that  it  is  a  fit  emblem  of  the  kingdom  of  purity 
and  peace.  And  when  the  setting  sun  lights  up 
the  evening  altar  in  the  West,  who  "can  repress 
the  rising  prayer  of  devotion,  and  hesitate  to  be- 
lieve, with  the  child,  that  his  Heavenly  Father  is 
smiling  behind  the  clouds  ?  There  is  a  depth  to  the 
beauty  of  nature  which  man  cannot  fathom.  Poetry 
cannot  describe  it,  and  the  highest  art  only  displays 


38  WAVE  THEORY. 


its  weakness  when  it  attempts  to  copy  it.  The 
savage  feels  that  it  is  immeasurably  above  him,  and 
worships  it.  The  artist  seeks  to  attain  it,  but  the 
more  he  strives,  the  more  it  surpasses  his  power, 
and  he  dies  disappointed,  unless,  happily,  he  finds 
that  the  perfect  ideal  has  been  realized  only  in 
Christ,  and  thus  through  nature  is  led  up  to  na- 
ture's God.  Yes !  the  beauty  of  nature  is  in  the 
Infinite  Presence  it  conceals,  and,  unconsciously 
though  it  may  be,  it  is  the  spirit,  not  the  matter, 
which  the  artist  loves. 

Such  are  some  of  the  evidences  of  design  which 
we  discover  in  the  relations  of  the  atmosphere  to 
light.  Let  us  now  examine  some  of  its  relations  to 
heat,  which  v/e  shall  find  not  less  instructive.  It 
was  formerly  supposed  that  the  rays  of  heat,  al- 
though accompanying  the  luminous  rays  in  the  sun- 
beam, were  essentially  different  from  those  of  light. 
But  it  is  now  almost  universally  believed  that  the 
rays  of  heat  differ  from  those  of  light  only,  at  most, 
as  one  color  differs  from  another,  and  that  even  the 
same  rays,  which,  falling  on  the  retina  of  the  eye, 
excite  the  sensation  of  light,  when  falling  on  the 
nerves  of  feeling  may  excite  heat.  But  what,  you 
may  ask,  is  the  difference  between  the  different 
colors?  The  subject  is  somewhat  abstruse,  but  if 
you  will  follow  me  attentively  for  a  few  minutes  I 
will  try  to  make  it  intelligible. 

Every  one  who  has  dropped  a  stone  into  the 
water  of  a  still  lake  has  noticed  the  system  of  waves 
which,  with  its  ever-increasing  circles,  spreads  in 
every   direction  from  the   stone  ;  but  all  may  not 


WAVES  OF  SOUND.  39 

know  that  when  two  stones  are  struck  together  in 
the  air  a  similar  system  of  aerial  waves  spreads,  in 
ever-widening  spheres,  through  the  atmosphere,  and 
that  it  is  these  waves  breaking  on  the  tympanum  of 
our  ears,  like  the  waves  of  water  on  a  sand-beach, 
which  produce  the  sensation  we  call  sound.  Two 
stones  thus  struck  together  give  rise  to  waves  of 
unequal  size,  following  one  another  at  irregular 
intervals  ;  and  such  waves  produce  an  unpleasant 
sensation  on  our  auditory  nerves,  which  we  call 
noise.  But  if,  instead  of  striking  together  two 
stones,  we  set  in  vibration  the  string  of  a  piano- 
forte or  the  reed  of  an  organ-pipe,  we  excite  a  sys- 
tem of  waves,  all  of  equal  size,  and  succeeding  one 
another  with  perfect  regularity,  and  these  breaking 
on  the  ear  produce  by  their  regular  beats  what  we 
call  a  musical  note.  If  the  waves  follow  one  another 
with  such  rapidity  that  one  hundred  and  twenty- 
eight  break  on  the  tympanum  every  second,  the 
note  has  a  fixed  pitch,  called  in  music  "  C  natural." 
If  the  waves  come  faster  than  this,  the  pitch  is 
higher,  and  if  less  rapidly  the  pitch  is  lower.  What 
we  are  all  familiar  with  as  a  pitch  of  a  musical  note 
depends,  then,  on  the  rapidity  with  which  the  waves 
of  sound  strike  the  ear,  and  may  evidently  be  meas- 
ured by  the  number  of  waves  breaking  on  the  tym- 
panum in  a  second. 

Our  ears  are  so  constituted  that  they  can  hear  a 
musical  note  only  when  within  certain  fixed  limits 
of  pitch,  differing  to  a  slight  extent  with  different 
individuals.  The  deepest  bass  note,  which  can  be 
heard,  as  such,  by  a  good  ear,  is  produced  by  about 


40  WAVES  OF  SOUND. 

eight  waves  in  a  second.  If  the  waves  strike  less 
rapidly  than  this,  they  are  perceived  as  distinct 
beats,  and  beginning  at  this  note  the  musical  scale 
ascends  to  a  note  caused  by  twenty-four  thousand 
waves  a  second,  which  is  the  highest  note  percepti- 
ble by  human  sense.  The  range  of  a  piano  gener- 
ally extends  from  a  note  produced  by  sixteen  waves 
in  a  second,  to  one  caused  by  one  thousand  and 
twenty-four  waves  in  a  second,  as  is  shown  by  the 
accompanying  table. 

DIMENSIONS   OF  WAVES   OF    SOUND. 

Tsint^  Length  of  waves  Number  of  waves 

IMotes.  °  -  striking  the  ear 

in  feet.  in  one  second. 

C— 3  70    16 

C— 2  35    32 

C— I  17.5   64 

Q   8.75  128 

Q   4.375 256 

C3   2.178 512 

C4   1.093 1,024 

Name  of  Note,               C,  D/     E,       F^  G^       A^         B^           Q 

Number  of  Waves,       I28  I44    160  I/Of  I92  2 1 3|  24O  '256 

Ratio  of  each  number)   ._  9             g            4  3             g            2.5.             ^ 

to  that  of  Note  C,     j  ^  "8            4           "3  "0-            3              8              2 

Sounds  of  the  highest  pitch,  like  the  cry  of  some 
insects,  become  disagreeable,  and  by  some  persons 
cannot  even  be  distinguished.  It  is  quite  possible 
to  produce  a  sound,  which,  though  painfully  shrill 
to  one  person,  shall  be  entirely  unheard  by  another. 


WAVES   OF  LIGHT.  4I 


Professor  Tyndall,  in  his  very  interesting  work  on 
the  glaciers  of  the  Alps,  relates  an  instructive  anec- 
dote of  this  sort,  which  I  give  in  his  own  lan- 
guage. 

"  I  once  crossed  a  Swiss  mountain  in  company 
with  a  friend  ;  a  donkey  was  in  advance  of  us,  and 
the  dull  tramp  of  the  animal  was  plainly  heard  by 
my  companion ;  but  to  me  this  sound  was  almost 
masked  by  the  shrill  chirruping  of  innumerable  in- 
sects, which  thronged  the  adjacent  grass  ;  my  friend 
heard  nothing  of  this,  it  lay  quite  beyond  his  range 
of  hearing.** 

There  may,  therefore,  be  innumerable  sounds  in 
nature  to  which  our  ears  are  perfectly  deaf,  although 
they  are  the  sweetest  melody  to  more  refined  senses. 
Nay,  more,  the  very  air  around  us  may  be  resound- 
ing with  the  hallelujahs  of  the  heavenly  host,  when  / 
our  dull  ears  hear  nothing  but  the  feeble  accents  of  i 
_pur  broken  prayers.  ^ 

We  have  been  studying,  my  friends,  the  nature 
of  sound,  in  order  to  comprehend  more  readily  the 
nature  of  light  and  heat,  for  the  phenomena  in- 
cluded under  these  names  are  produced,  like  the 
phenomena  of  sound,  by  waves ;  not,  however,  by 
waves  in  the  air,  but  by  waves  in  a  medium  which 
is  as  much  more  subtile  than  air  as  air  is  more  sub- 
tile than  water, — indeed,  a  medium  so  exceedingly 
thin  that  it  eludes  all  our  powers  of  chemical  anal- 
ysis ;  but  which,  as  we  assume,  pervades  all  space, 
and  this,  too,  whether  the  space  be  filled  or  not,  at 
the  same  time,  by  other  forms  of  matter.  We  call 
this  medium  '*  ether,'*  and  through  it  the  waves  of 


42  CAUSE   OF  COLOR. 

light  speed  with  an  inconceivable  rapidity.  Sound 
travels  i,ioo  feet  in  a  second,  but  a  wave  of  light 
spans  187,000  miles  in  the  same  time,  and  starting 
from  the  sun  on  its  journey  of  unnumbered  years, 
to  Sirius  or  Arcturus,  leaves  the  whole  solar  system 
behind  in  a  single  hour. 

Yet  great  as  is  the  difference  of  velocity,  the 
analogy  between  sound  on  the  one  side,  and  light  or 
heat  on  the  other,  is  complete.  Every  luminifer- 
ous  body,  like  this  candle-flame,  excites  in  the  ten- 
uous ether  a  system  of  waves,  which  spread,  in 
ever- enlarging  spheres,  with  the  immense  veloc- 
ity just  described ;  and  it  is  these  little  billows 
which,  passing  through  the  humors  of  the  eye,  and 
breaking  on  the  retina,  produce  the  sensation  we 
call  light,  or,  falling  on  the  skin,  excite  the  less  deli- 
cate nerves  of  feeling,  and  cause  the  sensation  of 
heat. 

Moreover,  the  difference  between  colors  is  of  pre- 
cisely the  same  kind  as  the  difference  between 
notes.  Red,  yellow,  green,  blue,  violet,  etc.,  are 
names  we  give  to  sensations  caused  by  waves  of 
ether  breaking  at  regular  intervals  on  the  retina. 
Color  corresponds  to  pitch,  and — what  may  seem  to 
you  incredible — we  are  able  to  calculate  from  actual 
measurements  the  number  of  waves  of  ether  which 
must  break  on  the  retina  in  a  second  in  order  to 
produce  the  sensation  of  a  given  color.  Here  are 
some  of  the  numbers,  and,  extravagant  as  they 
appear,  they  are  the  sober  results  of  science,  and 
have  been  as  accurately  determined  as  the  magni- 
tudes and  distances  of  astronomy. 


CAUSE   OF  COLOR.  43 


^^1^^^  Number  of  waves*  Number  of  waves  in  a  second. 

v.oiors.  jj^  ^^  inch. 

Red 39?ooo   447  i^iHio^  million. 

Orange 42,000   506 

Yellow 44,000    535 

Green 47,000    577 

Blue 51,000    022 

Indigo 54?ooo   658 

Violet 57,000    699 


It  is  actually  true,  that  when  we  are  receiving  the 
sensation  of  red  there  are  no  less  than  477  million 
millions  of  ether  waves  breaking  on  the  retina  of 
our  eyes  every  second.  And  more  than  this,  we 
have  measured  the  length  of  these  waves,  and  we 
know  that  the  length  of  a  wave  of  red  light  from 
crest  to  crest  is  -j^^oo  ^^  ^^  i^^h.  By  examining  the 
table  you  will  also  discover  that  the  sensation  of 
red,  as  compared  with  other  colors,  results  from  the 
smallest  number  of  waves,  and  that  these  waves  are 
comparatively  large.  On  the  other  hand,  the  sensa- 
tion of  violet  is  caused  by  the  largest  number  of 
waves,  which,  however,  are  proportionally  small  in 
size.     The  red  light,  therefore,  corresponds  to  low, 


*  A  given  wave-length  corresponds  to  each  point  on  the  line  of  the 
solar  spectrum,  to  be  described  further  on.  The  numbers  given  in  the 
table  are  to  be  regarded  merely  as  the  mean  values  for  each  color, 
measured  at  points  on  the  spectrum,  marked  by  certain  prominent 
dark  lines  called  Frauenhofer's  lines.  The  solar  spectrum,  as  seen 
with  a  powerful  spectroscope,  is  crossed  by  thousands  of  these  lines, 
which  have  a  fixed  position,  and  therefore  serve  to  mark  definite  points 
on  this  otherwise  continuous  band  of  blending  colors. 


44  THE   SOLAR  SPECTRUM. 

and  the  violet  to  high  notes  of  music,  and  between 
these  extremes  there  exists  every  gradation  of  pitch 
which  is  here  manifested  in  color. 

Waves  of  all  the  dimensions  given  in  the  table,  to- 
gether with  waves  of  every  possible  length  between 
certain  extremes, — which  are  far  wider  than  those 
indicated  above, — move  together  in  the  sunbeam, 
and  their  combined  impression  produces  the  sensa- 
tion of  white  light.  We  have  a  very  simple  way  of 
analyzing  the  sunbeam  and  separating  its  different 
color-producing  waves.  The  method  consists  in 
passing  the  sunbeam  through  a  glass  prism.  The 
prism  has  the  power  of  bending  the  beam  from  its 
rectilinear  direction ;  but  it  does  not  change  the  di- 
rection of  the  motion  of  all  the  waves  to  the  same 
extent.  The  longer  waves,  which  give  the  sensation 
of  red,  are  bent  from  their  course  much  less  than  the 
shorter  waves,  which  produce  the  sensation  of  vio- 
let, while  waves  of  an  intermediate  length  take  a 
course  between  the  two.  Hence,  after  emerging 
from  the  prism  the  directions  of  the  different  waves 
diverge,  and  if  we  receive  the  beam  of  light  thus 
analyzed,  on  a  screen,  the  various  color-producing 
waves  strike  the  screen  at  different  points  of  a  con- 
tinuous line.  A  more  or  less  narrow  band  on  the 
screen  will  thus  be  illuminated  with  lights  of  different 
colors  in  the  following  order — Red,  Orange,  Yellow, 
Green,  Blue,  Indigo,  Violet — and  this  beautiful  phe- 
nomenon is  familiar  to  almost  every  one  under  the 
name  of  the  solar  spectrum. 

Here,  where  we  have  the  whole  scale  of  colors 
spread  out  before  us,  the  analogy  of  light  to  sound 


COLOR  AND   MUSICAL  NOTES.  45 

becomes  still  more  evident.  As  there  are  persons 
who  cannot  hear  the  shrill  sound  of  some  insects,  so 
there  are  many  who  cannot  see  certain  colors  of  the 
spectrum,  and  as  there  are  unquestionably  innumer- 
able sounds  in  nature  which  are  inaudible  to  our 
ears,  so  there  are  innumerable  waves  in  the  ether 
which  are  powerless  to  produce  the  sensation  of 
light.  Moreover,  singular  as  it  may  seem,  we  have 
more  palpable  evidence  of  the  existence  of  these 
non-luminiferous  waves  than  we  can  obtain  in  the 
case  of  sound.  There  are  waves  in  the  ether  far 
smaller,  and  undulating  far  more  rapidly,  than  those 
which  produce  violet  light ;  so  small  that  they  do 
not  even  jar  the  nerves  of  the  retina,  but  which, 
nevertheless,  breaking  on  the  prepared  plate  of  the 
photographer,  leave  there  an  impression  which,  de- 
veloped by  his  skill,  becomes  a  beautiful  copy  of  na- 
ture or  of  art.  On  the  other  hand,  there  are  waves 
in  this  same  ether  so  large  that  the  delicate  retina 
cannot  vibrate  in  unison  with  their  rough  beats,  but 
which,  nevertheless,  breaking  on  the  surface  of  the 
skin,  disturb  the  coarser  nerves  of  feeling,  and  pro- 
duce the  glow  of  heat.  Most  of  the  waves  which  im- 
press the  optic  nerve  will  also  affect  the  nerves  of 
feeling ;  but  the  reverse  is  not  true,  for  many  of  the 
waves  which  produce  the  sensation  of  heat  are  far 
too  large,  and  undulate  too  slowly,  to  set  in  vibra- 
tion the  retina  of  the  eye. 

I  hope  that  I  have  been  able  to  make  clear  two 
points, — first,  that  light  and  heat  are  forms  of  mo- 
tion ;  second,  that  the  differences  in  the  phenomena 
which  have  been  referred  to  these  two  agents  are 


46  THE  ATMOSPHERE  AND   HEAT. 

simply  different  sensations  or  different  effects'^  pro- 
duced by  the  same  wave-motion.  It  would  be 
highly  interesting,  in  this  connection,  to  examine  the 
wonderfully  delicate  adjustments  and  to  follow  out 
the  peculiarly  intricate  motions  which  concur  to  pro- 
duce the  phenomena  of  light  and  heat ;  for  they  are 
in  themselves  most  striking  illustrations  of  the  wis- 
dom of  the  Creator.  But  this  w^ould  lead  us  too  far 
from  our  proposed  plan,  and  I  must  content  myself 
with  the  few  facts  already  given,  which  were  neces- 
sary to  illustrate  the  relations  of  the  atmosphere  to 
the  thermal  conditions  of  our  globe. 

From  the  principles  stated,  it  is  evident  that  the 
atrnosph^erejiiust  act  in  diffusing  heat,  just  aswejiai^^ 
seen  that  it  acts^  in  diffusing  light.  Indeed,  this  ef- 
fect is  one  of  the  thousand  conditions  on  which  the 
existence  of  organic  life  depends.  Were  it  not  for 
the  influence  of  the  atmosphere,  the  greatest  ex- 
tremes of  temperature  would  be  produced  by  the 
alternation  of   day   and  night,  and   even  were   the 

*  The  effects  of  expansion,  melting,  evaporation,  the  permanent 
elasticity  of  gases  and  vapors,  and  many  other  phenomena,  formerly 
referred  to  the  action  of  a  peculiar  agent  called  heat,  are  now  sup- 
posed to  be  the  result  of  the  motion  which  the  ether-waves  commu- 
nicate to  the  material  particles  of  the  bodies  on  which  they  strike 
or  through  which  they  are  transmitted.  To  understand  this,  we  must 
remember  that  the  molecules,  even  of  the  densest  solids,  are  supposed 
to  be  separated  from  each  other  by  comparatively  large  spaces  filled 
with  ether,  through  which  the  waves  of  heat  and  light  may  move  more 
or  less  freely,  just  as  the  waves  of  air  pass  between  the  branches  in  a 
forest.  Moreover,  as  the  waves  of  air  impart  motion  to  the  branches  of 
the  trees,  and  afterwards  are  kept  in  motion  by  the  waving  boughs, 
so  also  the  material  particles  of  a  body  may  set  in  motion  the  waves 
of  ether,  or  receive  motion  from  them  in  return. 


DIFFUSION   OF   HEAT.  4/ 

density  of  the  atmosphere  reduced  only  one-half,  the 
variation  would  be  so  great  as  to  render  the  exist- 
ence of  the  higher  forms  of  organic  life  impossible, 
except,  perhaps,  in  the  more  favored  regions  of  the 
earth. 

But  not  only  does  the  atmosphere  diffuse  the  heat 
of  the  sun's  rays,  it  also  acts,  and  even  more  effectu- 
ally, in  retaining  on  the  surface  the  heat  which  the 
earth  is  constantly  receiving  from  that  great  central 
luminary.  The  atmosphere  has  been  compared  to  a 
mantle,  and  the  comparison  is  just ;  for,  like  a  huge 
cloak,  it  envelops  the  earth  in  its  folds,  and  protects 
it  from  the  chill  of  the  celestial  spaces  through 
which  we  are  rushing  with  such  frightful  velocity. 
In  order  to  understand  how  a  thin  and  transparent 
medium  like  air  can  thus  act  to  keep  the  earth  warm, 
we  must  recur  to  some  of  the  facts  established  above. 

As  the  ether-waves,  breaking  on  the  eye  more  or 
less  rapidly,  produce  the  different  sensations  of  color, 
so  when  breaking  on  the  skin  they  occasion  analogous 
differences  in  the  sensation  of  heat,  which,  although 
not  so  accurately  distinguished,  because  the  sense  is 
less  delicate,  nevertheless  are  as  real  as  the  differ- 
ence between  a  low  and  sweet  musical  note,  and  one 
that  is  high  and  shrill.  There  are  waves  of  heat 
which  break  upon  our  nerves  of  feeling  like  the  shrill 
cry  of  the  cricket  on  the  ear,  and  seem  to  penetrate 
to  the  very  brain,  while  there  are  others  which  fall 
like  the  low  tones  of  an  organ,  diffusing  throughout 
the  system  a  genial  glow.  Such,  for  example,  is  the 
difference  between  the  heat  from  a  hard-coal  fire 
and  that  from  a  steam  radiator.     The  waves  of  the 


48  THE  ATMOSPHERE  A  CLOAK. 

first  sort,  from  their  small  size  and  rapid  motion,  can 
readily  pass  through  glass  and  other  transparent 
media,  when  the  large  waves  with  their  slow  motion 
are  in  a  great  measure  stopped. 

Now  it  is  found  that  the  sunbeam  is  chiefly  made 
up  of  waves  of  the  first  class,  which  are  therefore 
able  readily  to  penetrate  the  atmosphere  and  warm 
the  surface  of  the  earth.  The  earth  thus  warmed 
becomes  itself  a  hot  body,  surrounded  by  an  in- 
tensely cold  space,  and,  like  anvotherhot  body,  tends 
to  lose  its  heat  by  radiation.  /jBut  the  waves  of  heat 
which  the  earth^  sets  in  motion  are  of  the  second 
class,  long  and  slow  undulations,  and  these  are  in 
great  measure  arrested  by  the  atmosphere;  indeed,  as 
experiments  have  proved,  they  are  chiefly  absorbed 
by  the  lower  strata,f  in  which  we  live  and  move. 

Thus  it  is  that  the  atmosphere  keeps  us  warm ; 
and  if  you  desire  further  proof  of  the  correctness 
of  these  experimental  deductions,  ascend  any  high 
mountain,  and,  as  the  thickness  of  the  aerial  cover- 
ing above  you  is  diminished  by  the  elevation,  you 
will  find  that  the  chill  increases,  vegetation  slowly 
disappears,  and  before  long  you  will  reach  a  region 
of  eternal  snow  and  ice.  It  is  true  that  there  are 
other  causes  acting  to  lower  the  temperature  at  high 


*  The  pitch,  if  we  may  so  speak,  and  penetrating  power  of  the 
heat-waves  depend  on  the  temperature  of  the  body  by  which  they  are 
set  in  motion,  and  in  proportion  as  the  temperature  rises  the  pitch  is 
higher  and  the  penetrating  power  greater. 

f  Professor  Tyndall  has  shown  that  this  effect  is  due  almost  entirely 
to  the  aqueous  vapor  in  the  atmosphere,  which  is  present  in  greatest 
quantity  in  the  strata  nearest  to  the  earth. 


A  TRAP  TO   CATCH   THE   SUNBEAM.  49 

elevations,  but  the  one  just  noticed  is  by  far  the 
most  important,  as  well  as  the  primary  cause.  The 
effect  of  the  atmosphere  is  precisely  similar  to  that 
of  the  glass  panes  of  a  hot-house.  The  glass,  like 
the  atmosphere,  allows  the  rapidly  undulating  waves 
of  the  sun  to  pass,*  but  almost  "entirely  arrests  the 
large  and  slowly  undulating  billows  which  radiate 
from  the  vegetation  within.  They  are  each,  in  fact, 
a  trap  to  catch  the  sunbeam. 

The  atmosphere  not  only  thus  acts  in  diffusing  the 
sun's  rays,  and  retaining  the  heat  which  they  bring 
to  us,  but  it  also  subserves  an  equally  important 
end  in  distributing  their  genial  warmth  over  the 
whole  surface  of  the  earth,  thus  moderating  the 
climate  of  the  temperate  zone,  and  mitigating  the 
intense  heat  of  the  tropics.  Air,  like  all  gases,  is 
expanded  by  heat,  and  thus  rendered  specifically 
lighter,  and  on  this  simple  principle  all  our  methods 
of  warming  and  ventilating  are  based.  When  now 
it  is  remembered  that  the  atmosphere  under  the 
tropics  must  become  more  intensely  heated  by  the 
vertical  rays  of  the  sun  than  it  is  in  the  temperate 
zones,  the  result  will  be  obvious.  The  heated  air. 
rises,  and  the  cold  adr  rushes  in  from  the  North  and 
South  to  take  its  place.  Thus,  two  general  currents 
are  excited  in  the  aerial  ocean  of  each  hemisphere, 
one  on  the  surface  of  the  earth,  tending  towards  the 

*  In  the  sunbeam,  as  it  passes  through  space,  there  are  undoubt- 
edly waves  of  low  pitch  in  abundance,  but  these  are  almost  entirely 
arrested  by  the  atmosphere  before  reaching  the  surface  of  the  earth. 
It  has  been  estimated  that  of  the  heat  the  earth  receives  from  the  sun 
about  one-third  is  thus  absorbed. 
3 


50  DISTRIBUTION   OF  HEAT. 

equator,  and  another,  higher  in  the  atmosphere, 
tending  towards  the  poles.  These  currents,  how- 
ever, do  not  blow  due  North  or  South  ;  for  many 
causes  combine  to  turn  them  from  their  primitive 
directions. 

In  the  first  place,  the  rotation  of  the  globe  on  its 
axis  imparts  to  objects  on  the  surface  a  motion  from 
West  to  East,  varying  in  velocity  from  nothing,  at 
the  poles,  to  the  speed  of  a  cannon-ball,  at  the 
equator.  In  consequence  of  this,  a  mass  of  air 
moving  towards  the  equator  is  constantly  arriving 
at  a  point  on  the  surface  of  the  earth,  which  is 
moving  towards  the  East  more  rapidly  than  the 
point  it  has  just  left ;  and  as,  in  virtue  of  the  law  of 
inertia,  the  moving  mass  cannot  accommodate  itself 
instantaneously  to  the  increased  velocity,  it  is  left  a 
little  behind, — that  is,  a  little  to  the  West,  at  every 
step.  Hence,  the  lower  or  polar  currents  bend 
more  and  more  towards  the  West  as  they  approach 
the  equator,  acquiring  in  the  northern  hemisphere  a 
south-westerly,  and  in  the  southern  hemisphere  a 
north-westerly  direction  ;  and  the  currents  of  the 
two  hemispheres,  meeting  at  the  equator,  combine 
to  produce  the  great  trade-wind,  which,  in  the  Pa- 
cific Ocean,  blows  constantly  from  the  East  to  the 
West,  and  would  blow  regularly  in  this  direction  all 
round  the  globe  if  the  continents  did  not  intervene 
to  disturb  its  course  at  various  points. 

The  effect  of  the  earth's  rotation  on  the  current 
of  warm  air  which  flows  from  the  equator  in  the 
upper  atmosphere,  must  evidently  be  the  reverse  of 
that  just   described,  bending  it  constantly  to  the 


TRADE- WINDS.  5 1 


East,  and  giving  to  it  in  the  northern  hemisphere  a 
north-westerly,  and  in  the  southern  hemisphere  a 
south-easterly,  direction.  But  the  upper  and  lower 
currents  do  not  long  retain  this  relative  position  ; 
for,  as  the  first  comes  northward,  it  gradually  sinks, 
and,  long  before  reaching  this  latitude,  touches  the 
surface  of  the  earth.  Then,  of  course,  it  comes  in 
collision  with  the  current  from  the  North,  and  here 
a  strife  for  the  mastery  ensues.  Sometimes  the  one 
and  sometimes  the  other  prevails,  and  this  alternat- 
ing ascendency  is  one  of  the  chief  causes  which  ren- 
der the  winds  of  temperate  climates  so  irregular. 

Again,  the  unequal  heating  effect  of  the  sun*s 
rays  on  the  earth,  as  compared  with  the  sea,  com- 
bined with  the  irregular  distribution  of  land  and 
water  over  the  surface  of  the  globe,  tends  to  com- 
plicate still  further  the  motion  of  the  aerial  currents. 
For  reasons  which  will  hereafter  appear,  the  land  is 
more  quickly  heated  by  the  sun*s  rays  than  the  sea, 
when  under  the  same  conditions,  and,  on  the  other 
hand,  as  soon  as  the  sun  is  withdrawn,  it  cools  more 
rapidly.  Hence,  on  an  island  in  a  warm  climate  we 
generally  have,  during  the  daytime,  a  current  of 
heated  air  rising  from  the  surface  of  the  earth,  and 
a  current  of  cooler  air  flowing  in  on  all  sides  from 
the  ocean  to  take  its  place,  while  after  sunset  the 
land  soon  cools  below  the  temperature  of  the  sur- 
rounding ocean,  and  the  current  is  reversed.  Thus 
is  produced  the  daily  alternation  of  land  and  sea 
breezes,  so  familiar  to  every  one  who  has  visited  the 
tropics,  where  the  phenomena  are  most  strongly 
marked. 


52  MONSOONS. 


Quite  a  similar  reciprocal  action  between  the  con- 
tinents and  the  great  ocean  is  caused  by  the  alter- 
nation of  seasons,  and  of  this  the  monsoons  of  the 
Indian  Ocean  are  a  remarkable  illustration.  This 
mediterranean  ocean,  shut  off  from  the  influence  of 
the  general  trade-winds  by  the  great  continental 
masses  which  surround  it,  has  a  system  of  aerial 
currents,  peculiar  to  itself,  blowing  six  months  of 
the  year  in  one  direction  and  six  months  in  the 
other.  These  are  set  in  motion  by  the  unequal 
heating  of  the  continents  of  Asia  and  Africa  during 
the  extreme  seasons.  In  the  months  of  December, 
January,  and  February,  the  part  of  Africa  south  of 
the  equator  is  exposed  to  the  vertical  rays  of  a 
summer's  sun,  while  the  countries  of  southern  Asia 
are  feeling  the  comparative  cold  of  their  winter. 
The  natural  consequence  is,  that  a  stream  of  cold  air 
rushes  across  the  Indian  Ocean  to  feed  the  intensely- 
heated  current  which  is  rising  over  the  burning 
plains  of  Africa,  and  produces  a  strong  north-east- 
erly breeze,  which  is  the  winter  monsoon  of  India. 
When,  however,  the  sun  comes  north  of  the  equa- 
tor, all  these  conditions  are  reversed.  The  ocean 
air  now  rushes  to  the  more  heated  plains  of  India, 
and  tlie  summer  monsoon  sets  in,  which  blows  from 
the  south-west,  the  change  from  one  to  the  other 
being  always  attended  by  variable  winds  and  furi- 
ous storms.  Lastly,  the  position  of  mountain  chains 
and  the  configuration  of  the  continents,  which  break 
and  turn  the  winds,  or  open  to  them  a  freer  chan- 
nel, have  an  important  influence  in  determining  the 
direction  of  the  aerial  currents  on  the  earth. 


AERIAL  CURRENTS.  S3 

But  we  have  not  time  for  further  details  ;  they  are 
given  in  all  works  on  physical  geography,^  and  the 
student  of  natural  theology  will  find  that  subject  rich 
in  illustrations  of  God's  wisdom  and  power.  We 
have  already  become  sufficiently  acquainted  with  the 
general  plan  to  understand  how  the  atmosphere  acts 
in  equalizing  the  climate  of  the  globe.  The  aerial 
currents  which  come  to  us  from  the  South  bring 
with  them  the  heat  of  the  tropics,  and  distribute  it 
over  the  temperate  zone.  As  they  blow  from  the 
south-west,  they  naturally  exert  the  greatest  heating 
power  on  the  western  coasts  of  the  continents,  and 
this  is  one  great  cause  of  the  well-known  fact  that 
the  climate  of  western  Europe  is  so  much  milder 
than  our  own,  and  the  climate  of  California  and 
Oregon  so  much  warmer  than  that  of  the  corre- 
sponding latitudes  on  the  eastern  coast  of  Asia. 
Moreover,  the  sea-breezes  on  islands  and  along  sea- 
coasts,  the  monsoons  of  the  Indian  Ocean,  and 
other  local  currents,  all  combine,  as  our  theory 
shows,  to  produce  the  same  general  result,  cooling 
such  regions  of  the  earth  as  from  any  cause  have 
become  overheated,  and  transferring  the  warmth  to 
places  where  it  is  more  needed.  Just  as  the  heat 
of  burning  fuel  is  diffused  over  a  whole  building 
from  the  furnace  by  the  currents  of  air  it  sets  in 
motion,  so  the  sun's  heat  is  diffused  over  the  earth 
from  the  tropics  by  the  great  terrestrial  currents  we 
have  so  briefly  described.  Indeed,  as  already  stated, 
in  all  our  methods  of  heating,  we  merely  apply,  on 

*  See  Earth  and  Man,   by  Professor  Arnold  Guyot. 


54  CAPACITY  FOR  HEAT. 

a  small  scale,  the  same  general  principles  which  are 
at  work  around  us  in  the  atmosphere. 

But,  although  the  heat  of  the  sun  might  set  in  mo- 
tion these  aerial  currents,  they  would  have  but  little 
effect  in  warming  our  northern  climate,  were  it  not 
that  the  air  has  been  endowed  with  a  certain  capac- 
ity for  holding  heat.  All  substances  possess  this 
capacity  to  a  greater  or  less  degree,  but  the  differ- 
ences between  them  are  very  large.  Thus  the 
amount  of  heat  required  to  warm  a  pound  of  water 
is  ten  times  greater  than  would  be  required  to  raise 
the  temperature  of  a  pound  of  iron,  and  thirty  times 
greater  than  would  be  required  to  raise  the  temper- 
ature of  a  pound  of  mercury  to  an  equal  extent. 
Hence,  under  the  same  conditions,  a  pound  of  water 
may  be  said  to  contain  ten  times  as  much  heat  as  a 
pound  of  iron,  and  thirty  times  as  much  as  a  pound 
of  mercury ;  or,  again,  in  other  words,  the  capacity 
of  water  for  heat  is  ten  times  greater  than  that  of 
iron,  and  thirty  times  greater  than  that  of  mercury. 
The  capacity  of  air  for  heat  is,  weight  for  weight, 
about  twice  as  great  as  that  of  iron,  and  although 
only  one-fifth  as  great  as  the  capacity  of  water,  it  is 
yet  greater  than  that  of  most  other  substances.  .  The 
point,  however,  to  which  I  wish  to  direct  your  atten- 
tion, is  the  fact  that  this  capacity  is  exactly  adjusted 
to  the  office  which  the  air  has  been  appointed  to  filL 
Were  the  capacity  of  the  air  less,  the  hot  air  from 
the  tropics  would  bring  to  us  proportionally  less 
heat ;  were  it  greater,  the  reverse  would  be  the  case  ; 
and  in  either  event,  the  distribution  of  temperature 
on  the  earth  would  be  changed.     To  what  extent 


THE  ATMOSPHERE  AND   ELECTRICITY.  55 

such  a  change  would  affect  the  general  welfare  of 
man,  it  is  impossible  to  determine  ;  but  when  we 
consider  how  far  the  history  of  man  has  been  influ- 
enced by  climate,  it  will  appear  that  the  present  dis- 
tribution of  the  human  race — the  existence,  for  ex- 
ample, of  a  large  and  influential  city  in  this  place — 
may  be  said  to  depend  on  the  adjustment  of  the 
capacity  of  the  atmosphere  for  heat ;  and  yet  it  de- 
pends no  less  on  ten  thousand  other  conditions, 
many  of  them  far  more  important  than  this.  How 
truly,  then,  it  may  be  said,  that  even  here  on  earth 
we  live  in  '^  a  city  which  hath  foundations,  whose 
builder  and  maker  is  God  '* ! 

Such  are  a  few  of  the  more  obvious  marks  of  de- 
sign, which  may  be  discovered  by  studying  the 
relations  of  the  atmosphere  to  light  and  heat.  I 
might  here  close  one  division  of  my  subject ;  but  I 
should  fail  to  give  you  an  adequate  idea  of  the 
wonderful  play  of  physical  forces  in  the  atmosphere, 
were  I  to  leave  out  of  view  that  mighty  agent  which 
charges  the  artillery  of  heaven  and  feeds  the  flam- 
ing torches  in  the  northern  sky.  It  is  true  that  the 
atmospheric  relations  of  electricity  are  very  imper- 
fectly understood,  and  the  important  ends  which  it 
undoubtedly  subserves  in  the  economy  of  nature 
almost  entirely  unknown.  We  cannot,  therefore, 
expect  them  to  furnish  us  with  many  additional 
illustrations  of  the  Divine  attributes  ;  but  since  elec- 
trical phenomena  play  so  conspicuous  a  part  in  the 
atmosphere,  and  must  have  been  included  in  its 
plan,  they  certainly  should  not  be  overlooked  if  we 


56  THEORY  OF  ELECTRICITY. 

would  gain  a  general  idea,  however  imperfect,  of  the 
whole  design. 

Of  all  the  assumed  agents  of  nature  there  is  hardly- 
one  which  is  so  little  understood,  and  yet  has  been 
so  carefully  studied,  as  electricity.  To  the  unedu- 
cated it  affords  the  convenient  explanation  of  most 
obscure  phenomena,  while  with  men  of  science  it 
is  the  object  of  much  laborious  investigation  and 
careful  theorizing.  The  study  of  its  phenomena 
has  been  fruitful  in  the  discovery  of  facts  ;  but  it 
has  as  yet  led  to  but  few  general  principles,  and  has 
furnished  only  a  meagre  explanation  of  those  grand 
displays  of  nature  in  which  it  seems  to  be  such  an 
important  agent. 

In  regard  to  the  nature  of  electricity,  we  are  en- 
tirely ignorant.  The  phenomena  of  light  and  heat* 
admit,  to  say  the  least,  of  an  intelligible  explana- 
tion, and  can  be  referred  to  a  dynamical  origin  ; 
but  in  the  case  of  electricity  we  are  obliged  to  be 
content  with  collecting  facts,  and  must  await  the 
further  progress  of  science  to  reveal  the  now  hidden 
cause.  I  am  well  aware  that  electricity  has  been  re- 
garded as  a  very  rare  and  subtile  "  fluid,'*  and  that  this 
theory  has  not  only  afforded  a  plausible  explanation 
of  most  of  the  phenomena  of  statical  electricity,  but 
also  that  the  numerical  results  based  upon  it  have 
been  most  remarkably  verified  by  experiment.  Yet 
nevertheless,  although  the  theory  may  still  be  used 
as  a  convenient  frame  in  which  to  exhibit  the  facts, 
there  are  but   few  investigators  of  the  present  day 

*See  Tyndall's  "  Heat  Considered  as  a  Mode  of  Motion." 


FUNDAMENTAL  FACTS.  57 

who  would  claim  for  it  more  than  a  very  partial 
foundation  in  truth,  and  most  would  reject  it  alto- 
gether as  utterly  untenable. 

The  fundamental  facts  of  electricity  were  known 
to  the  ancients,  and  are  familiar  to  every  one.  If  a 
stick  of  sealing-wax  or  a  glass  tube  be  rubbed  with 
a  warm  silk  handkerchief,  it  becomes,  as  we  say, 
electrified,  and  in  this  condition  has  the  power  of 
attracting  pieces  of  paper  or  any  light  particles  of 
matter.  When  the  scientific  men  of  the  last  cen- 
tury came  to  examine  these  phenomena  more  care- 
fully, they  found  that  the  handkerchief  was  also 
electrified,  and  thrown  into  a  state  differing  from 
that  of  the  glass  in  the  one  case,  and  that  of  the  re- 
sin in  the  other,  very  much  as  the  north  pole  of  a 
magnet  differs  from  its  south  pole.  They  found,  also, 
that  the  resin  was  electrified  oppositely  to  the  glass, 
and  they  hence  concluded  that  there  were  two  kinds 
of  electricity,  which  they  distinguished  by  the  names 
resinous  and  vitreous,  or  positive  and  negative. 
They  also  discovered  that  this  agent  could  readily 
be  drawn  off  from  electrified  bodies  by  the  metals, 
but  only  with  difficulty,  if  at  all,  by  such  materials 
as  india-rubber,  glass,  resin,  or  silk,  and  they  were 
hence  led  to  divide  substances  into  conductors  and 
non-conductors  of  electricity.  A  good  conductor, 
when  insulated  by  non-conductors,  was  found  to  re- 
tain for  a  short  time  the  electricity  it  had  received 
from  the  electrified  glass  or  resin,  although  the 
charge  was  soon  dissipated  by  the  surrounding  air, 
especially  when  moist.  By  bringing  in  the  aid  of 
machinery,  and  thus  increasing  the  surface  of  fric- 
3* 


S8  FUNDAMENTAL   FACTS. 

tion,  it  was  found  possible  to  enhance  very  greatly 
the  effects  obtained  with  a  glass  tube ;  and  this  was 
the  origin  of  the  electrical  machine.  This  familiar 
instrument  is  merely  a  mechanical  contrivance  for 
rubbing  together  glass  and  silk,  with  two  insulated 
metallic  conductors  for  receiving  the  two  kinds  of 
electricity  thus  generated.  If  the  hand  or  a  metallic 
knob  was  brought  near  the  prime  conductor  of  the 
machine  when  highly  electrified,  it  was  found  that  a 
luminous  discharge  followed,  which  was  termed  an 
electrical  spark ;  and  it  was  found  possible  by  means 
of  a  glass  vessel,  coated  inside  and  outside  with  some 
metallic  leaf,  called  a  Leyden  jar,  to  accumulate  the 
two  electricities  in  such  large  quantities  that,  when 
allowed  to  flow  together,  the  discharge  was  capable 
of  producing  violent  mechanical  action,  similar  to 
that  of  lightning,  although  on  a  vastly  reduced  scale. 
It  was  also  discovered  that  electricity  passes  readily 
through  the  greatly  rarefied  atmosphere  in  the  re- 
ceiver of  an  air-pump,  causing  a  luminous  effect  sim- 
ilar to  the  aurora  borealis.  Lastly,  it  was  observed 
that  electricity  readily  escapes  into  the  atmosphere 
from  a  pointed  conductor,  and,  conversely,  that  a 
heavy  charge  can  be  silently  and  harmlessly  drawn 
from  an  electrified  body  by  holding  near  it  the  point 
of  a  needle.  By  attaching  a  pointed  conductor  to 
a  boy*s  kite,  Franklin  succeeded  in  drawing  an  elec- 
tric spark  from  a  thunder-cloud,  and  having  thus 
established  the  identity  between  atmospheric  and 
frictional  electricity,  he  erected  the  pointed  rod, 
which  protects  our  dwellings  against  the  lightning  s 
stroke. 


FUNDAMENTAL  FACTS.  59 

More  recently  it  has  been  discovered  that  friction 
is  by  no  means  the  only  source  of  electricity,  and  it 
seems  probable  that  no  change^  either  chemical  or 
physical,  takes  place  in  nature  without  some  mani- 
festation of  this  agent.  It  was  at  first  supposed 
that  there  were  several  kinds  of  electricity,  which 
w^ere  named  thermo-electricity,  magneto-electricity, 
voltaic  electricity,  and  animal  electricity,  according 
to  the  nature  of  the  process  in  which  the  electrical 
action  was  developed  ;  but  it  is  now  universally 
conceded  that  all  are  only  different  manifestations 
of  the  same  agent,  and  most  investigators  believe 
that  electricity  will  in  time  be  shown  to  be  a  form 
of  molecular  motion  analogous  to  that  which  pro- 
duces the  phenomena  of  hght  and  heat,  although  it 
has  not  as  yet  been  found  possible  to  frame  a  com- 
prehensive and  intelligible  theory  based  upon  this 
hypothesis.  Again,  it  has  been  found  that  friction 
is  a  far  more  general  source  of  electricity  than  was 
at  first  believed.  In  fact,  electrical  phenomena  ap- 
pear to  be  a  constant  result  of  friction,  whatever 
may  be  the  nature  of  the  substances  rubbed.  Thus 
it  is  developed  by  blowing  air  over  glass,  and  the 
hydro-electric  machine,  one  of  the  most  effective 
means  of  generating  electricity  we  possess,  owes 
its  surprising  energy  to  the  friction  of  globules  of 
water  against  the  sides  of  the  vent-cock  of  a  steam- 
boiler."^ 

When,  now,  we  consider  that  the  air   is  always 

*  This  machine  consists  simply  of  a  small  steam-boiler  insulated  on 
glass  pillars,  having  a  peculiarly-constructed  vent-cock  and  provided 
with  suitable  metallic  conductors  for  receiving  the  electricity.     The 


6o  ATMOSPHERIC   ELECTRICITY. 

rubbing  over  the  surface  of  the  earth,  at  times  with 
great  rapidity,  we  shall  not  be  surprised  to  learn 
that  both  bodies  are  constantly  in  an  electrified 
condition,  the  earth  being  generally  charged  nega- 
tively, and  the  atmosphere  positively.  Even  in  fair 
weather  it  is  always  possible  to  detect  the  presence 
of  free  electricity  in  the  atmosphere ;  and  during  a 
storm,  when  clouds  filled  with  drops  of  water  are 
hurried  over  the  surface,  grinding  against  the  hills 
and  the  trees,  or  against  each  other,  the  atmos- 
phere becomes  a  vast  hydro-electric  machine,  whose 
sparks  are  the  lightning,  and  the  noise  of  whose 
discharges  the  thunder.  Again,  the  various  chemi- 
cal and  physical  changes  which  are  going  on  around 
us, — such  as  the  vital  processes  of  animals  and 
plants,  the  combustion  of  fuel,  volcanic  action,  the 
evaporation  of  water, — all  undoubtedly  add  to  the 
electrical  excitement  of  the  atmosphere,  and  more 
or  less  modify  the  result.  It  is  not  important  for 
us,  however,  to  study  the  action  of  each  one  of 
these  causes  ;  for  we  have,  probably,  in  the  friction 
of  moist  air  driven  by  the  winds,  the  chief  source  of 
atmospheric  electricity ;  and  when  we  consider  the 
amount  of  friction  which  must  attend  the  rapid 
motion  of  storm-clouds,  or  of  a  tori^ado  through  the 
atmosphere,  the  wonder  is,  not  that  an  occasional 
thunderbolt  should  kindle  a  conflagration,  or  even 
cause  a  death,  but  that  every  storm  does  not  lay 
waste  the  earth  along  its  fiery  track.      Moreover, 

steam,  as  it  escapes  under  high  pressure,  becomes  filled  with  globules  of 
water  which  rub  against  the  sides  of  the  vent-tube,  and  this  is  so 
shaped  as  to  facilitate  their  formation. 


PROTECTION  AGAINST   LIGHTNING.  6l 

when  we  appreciate  the  vastness  of  the  scale  on 
which  the  electrical  machine  of  nature  is  constructed, 
the  thunder-storm  ceases  to  surprise  us,  and  only 
calls  our  attention  to  those  beneficent  provisions  by 
which  we  and  our  race  are  saved  by  a  constant 
miracle  from  the  fate  of  the  cities  of  the  plain. 
That  the  atmospheric  electricity  was  designed  to 
subserve  many  important  and  beneficent  ends,  the 
whole  analogy  of  nature  compels  us  to  believe ;  but 
while  our  present  ignorance  conceals  them  from  our 
sight,  we  may  still  discover  evidence  of  God's  good- 
ness and  wisdom  in  those  simple  provisions  by  which 
the  atmosphere  is  preserved  from  violent  or  frequent 
electrical  excitements,  and  its  charge  drawn  down 
harmlessly  to  the  earth. 

Since  the  atmosphere  is,  at  best,  a  very  poor  con- 
ductor, the  electricity  developed  by  the  processes 
just  considered  tends  to  accumulate ;  and  under  pe- 
culiar conditions  the  clouds  may  become  so  highly 
charged,  that  at  length  the  pent-up  power  acquires 
sufficient  force  to  break  through  all  barriers,  and 
the  lightning  dashes  to  the  earth,  crashing,  rending, 
and  burning  on  its  way.  To  guard  his  roof  from  its 
destructive  action,  man  erects  the  lightning-rod, 
whose  bristling  points  quietly  drain  the  clouds,  or, 
failing  to  do  this,  receive  the  charge,  and  bear  it 
harmlessly  to  the  earth.  But  ages  before  Franklin 
pointed  the  first  rod  to  the  storm,  the  Merciful  Par- 
ent of  mankind  had  surrounded  the  dwellings  of 
his  children  with  a  protection  far  more  effectual  than 
this;  for,  since  jdie  creation  of  organic  life,  every 
pointed  leaf,  every  twig,  and  every  blade  of  grass 


62  PROTECTION  AGAINST  LIGHTNING. 

has  been  silently  disarming  the  clouds  of  their  de- 
structive weapon.  It  is  difficult  to  improve  upon 
nature,  and  man  constantly  finds  that  in  his  best 
inventions  he  hasTieen  anticipated  from  eternity  by 
an  Inventor  greater  than  himself.  So,  not  long  after 
Franklin  had  discovered  the  efficacy  of  metallic  points 
in  dissipating  charges  of  electricity,  and  had  applied 
the  principle  in  constructing  the  lightning-rod,  it  was 
found  that  a  common  blade  of  grass,  sharpened  by 
nature's  exquisite  workmanship,  was  three  times  as 
effectual  to  the  end  in  view  as  the  finest  cambric 
needle,  and  a  single  twig  far  more  efficient  than  the 
metallic  point  of  the  best-constructed  rod.  When, 
now,  you  reflect  how  many  thousands  of  these  vege- 
table points  every  large  tree  directs  to  the  sky,  and 
consider  what  must  be  the  efficacy  of  a  single  forest 
with  its  innumerable  twigs,  or  of  a  single  meadow 
with  its  countless  blades  of  grass  ;  when  you  remem- 
ber that  these  are  only  subsidiary  to  those  vast  light- 
ning-conductors the  mountain-chains,  whose  craggy 
summits  pierce  the  clouds  themselves  ;  and  still  fur- 
ther, when  you  learn  that  rain-drops  and  snow- 
flakes  also  have  been  made  good  conductors,  so  that 
during  storms  a  natural  bridge  for  the  lightning 
reaches  across  from  the  clouds  to  the  earth,  you 
will  see  how  abundant  the  protection  is,  and  with 
what  care  Providence  has  guarded  us  from  the  de- 
structive agent.  It  is  only  under  unusual  circum- 
stances, when  electricity  is  developed  more  rapidly 
than  it  can  be  dissipated  through  these  numberless 
channels,  that  a  violent  discharge  takes  place,  and 
if  then   it  tears,  burns,  or  kills,  it  also  reveals  the 


MARKS   OF  DESIGN.  63 

Merciful  Hand  which  constantly  spares.  Moreover, 
through  this  servant  of  his  pleasure,  God  is  con- 
stantly educating  and  elevating  his  creatures.  In 
the  wild  coruscations  of  the  lightning,  and  in  the 
reverberating  roll  of  the  thunder.  Nature  exhibits 
one  of  her  grandest  aspects,  and  when,  through  the 
cold,  dry  air  of  the  polar  region  the  electric  charges 
shoot  down  to  the  earth  in  tremulous  flashes,  we 
see  her  lighting  up  those  grand  displays  of  northern 
fire  which  enliven  the  long  night  of  the  arctic  win- 
ter, or  in  this  more  favored  climate  excite  the  admi- 
ration of  all.*^ 

I  must  here  conclude  this  very  imperfect  sketch 
of  the  physical  adaptations  of  the  atmosphere  to  the 
ends  it  subserves  on  the  earth.  We  studied  in  the 
first  place  its  aeriform  condition,  and  found  that  its 
density  not  only  formed  an  essential  part  of  the 
scheme  of  organic  nature,  but  also  was  closely  related 
to  the  dimensions  of  the  solar  system.  In  this  Lec- 
ture we  have  studied  the  relations  of  the  atmosphere 
to  light,  heat,  and  electricity ;  and  although  we  have 
been  able  only  to  glance  at  some  of  the  more  prom- 
inent features  in  these  wonderful  displays  of  .  crea- 
tive energy,  we  have  found,  wherever  we  turned, 
abundant  illustrations  of  the  wisdom,  power,  and 
goodness  of  our  God.  I  trust  that  you  have  been 
impressed  by  the  vastness,  the  complexity,  and  yet 

*  I  am  indebted  for  many  of  the  above  illustrations  to  an  admirable 
paper  on  atmospheric  electricity,  in  the  American  Almanac  for  1854, 
by  my  friend  and  colleague  Prof.  Joseph  Lovering. 


64  MARKS  OF  DESIGN. 

the  simplicity  and  harmony  of  the  whole  design,  for 
these  are  the  chief  points  which  I  have  endeavored 
to  set  forth.  But  oh  how  imperfect  any  conception 
which  I  can  give  you  must  be !  This  atmosphere  is 
sustained  in  the  proper  working  of  all  its  parts  only 
by  the  exact  balancing  of  a  thousand  conditions. 
Attempt  to  make  yourself  acquainted  with  these 
conditions,  and,  disregarding  those  which  you  re- 
cognize at  once  as  surpassing  human  intelligence, 
study  only  such  as  are  thoroughly  understood  and 
universally  admitted  to  have  been  primary  con- 
ditions in  the  plan  of  nature  before  the  atmosphere 
could  exist  as  it  is.  This  is  not  an  impossible  task. 
It  would  require  years  of  study  and  it  would  lead 
you  into  every  department  of  physical  science,  but 
the  result  would  well  repay  your  labor.  You  would 
find  it  easy  to  follow  out  any  one  line  of  the  con- 
ditions, until  it  became  lost  in  the  obscurity  of  the 
unknown  ;  but  to  form  an  adequate  conception  of  the 
simultaneous  working  of  all  the  conditions  in  their 
varied  bearings,  or  even  of  two  or  three  of  them,  you 
would  soon  discover  to  be  a  hopeless  task.  The  com- 
plication of  this  wonderful  machinery  so  far  tran- 
scends man's  insight,  that  to  understand  its  com- 
bined action  is  simply  impossible.  But  although  thus 
made  keenly  sensible  of  the  limits  of  human  thought, 
you  would  be  filled  with  gratitude  for  the  high  priv- 
ilege enjoyed  of  studying  the  divine  mechanism,  even 
though  you  understood  its  workings  only  obscurely 
and  in  part. 

^aley  has  compared  the  mechanism  of  nature  to 
a  wStch,  and,  so  far  as  the   argument  for  design  is 


MARKS   OF  DESIGN.  65 

concerned,  the  analogy  is  perfect.  We  must  never 
forget,  however,  that  there  is  an  essential  difference 
between  the  scheme  of  nature  and  the  most  compli- 
cated human  mechanism.  I  have  seen  a  carpet- 
loom  weaving  a  pattern  composed  of  twelve  differ- 
ent colors,  and,  as  I  watched  the  shuttles  of  various 
colored  yarns  which  were  selected  by  the  hands  of 
the  machine  with  unerring  certainty,  and  thrown 
through  the  warp,  it  seemed  as  if  the  very  iron  were 
endowed  with  intelligence,  and  the  impression  was 
one  of  wonder  and  bewilderment.  To  comprehend 
such  complexity  appeared  impossible ;  but  the  more 
I  studied  the  details  of  the  machine,  the  more 
thoroughly  I  understood  the  mode  of  its  action, 
until  at  last  the  wonder  vanished;  and  although 
not  ceasing  to  admire  the  skill  of  the  inventor,  I  felt 
that  I  had  comprehended  the  whole,  and  could  even 
conceive  of  the  mental  process  by  which  such  a 
wonderful  combination  of  means  had  been  thought 
out  and  adjusted  to  produce  the  desired  end.  The 
artist  was  ingenious,  but  the  machine  was  still 
human. 

How  different  it  is  with  the  mechanism  of  na- 
ture!  Here,  also,  it  is  true,  the  more  we  study, 
the  more  we  understand  the  workmanship ;  but 
then  we  never  reach  the  limit.  The  more  our 
powers  of  thought  and  observation  are  developed, 
and  the  more  our  experience  is  enlarged,  the  more 
the  field  of  possible  knowledge  expands  before  us. 
The  larger  our  attainments,  the  less  we  seem  to 
know. 

We  still  recognize  the  unmistakable  marks  of  in- 


(£  MARKS   OF  DESIGN. 

telligence  in  the  design,  but  it  is  no  longer  a  fathom- 
able intelligence ;  we  feel  that  it  is  infinitely  above 
us :  in  a  word,  we  feel  that  it  is  God.  Would  that 
my  feeble  language  might  convey  to  you  the  full 
power  of  this  impression  ;  for  until  one  has  become 
conscious  of  the  infinite  beauty  and  skill  with  which 
the  numberless  parts  of  nature  have  been  fashioned 
and  adjusted,  one  cannot  appreciate  the  force  of 
the  conviction  which  the  impression  gives.  We 
may  make  ourselves  familiar  with  the  dimensions  of 
Mont  Blanc  ;  we  may  read  the  most  glowing  descrip- 
tions of  this  "  monarch  of  mountains,"  heightened 
by  all  the  arts  of  eloquence  or  of  poetry ;  we  may 
cross  the  ocean  and  travel  to  the  beautiful  valley  of 
Chamouni  at  its  base ;  we  may  even  climb  its  side, 
study  its  glaciers,  and  cross  its  fields  of  snow  :  but 
we  can  form  no  adequate  conception  of  its  gran- 
deur, until,  ascending  one  of  the  lofty  mountain- 
peaks  which  surround  it,  we  see  its  summit  still 
towering  above  our  heads,  apparently  higher  than 
before.  So  it  is  in  the  study  of  nature.  No  de- 
scription can  convey  an  adequate  conception  of  the 
impression  which  it  leaves  upon  the  mind.  It  is  not 
until  the  student,  after  long  study,  has  become  thor- 
oughly acquainted  with  some  one  portion,  however 
limited,  of  its  wonderful  economy,  that  he  begins  to 
appreciate  the  perfection  of  its  parts,  the  infinite 
skill  with  which  all  have  been  adjusted,  and  the  true 
grandeur  of  the  w^hole. 

By  most  men  these  heights  of  knowledge  are  un- 
attainable. Why,  then,  should  we  hesitate  to  receive 
the   evidence   of   a  philosopher  like  Newton,  who. 


MARKS   OF  DESIGN.  6/ 

after  spending  a  long  life  in  the  investigation  of 
nature,  and  with  a  success  unparalleled  in  the  history 
of  science,  uttered  this  memorable  sentiment  shortly 
before  his  death  :  ^^^  I  do^or~1mow  whM  I  rhay 
pear  to  the  world  ;  but  to  myself  I  seem  to  have 
been  only  like  a  boy  playing  on  the  sea-shore,  and 
devoting  myself  now  and  then  to  finding  a  smoother 
pebble  or  a  prettier  shell  than  ordinary,  while  the 
great  ocean  of  truth  lay  all  undiscovered  before  me."  j 
I  know  this  sentiment  has  been  so  many  times  re- 
peated as  to  seem  trite,  but,  coming  from  whom  it 
does,  it  cannot  be  too  often  quoted.  It  is  the  testi- 
mony of  the  foremost  master  of  science  to  its  great- 
est and  sublimest  truth. 

We  can  all  recognize  the  marks  of  design  in  na- 
ture, and  when  we  add  to  this  evidence  of  our  senses 
the  testimony  of  a  man  like  Newton,  who  assures  us 
that  the  more  our  powers  are  enlarged,  and  the 
wider  our  knowledge  becomes,  the  grander  and 
vaster  the  design  will  appear,  until  it  surpasses  all 
our  powers  of  thought  or  imagination,  we  begin  to 
feel  the  full  depth  of  the  truth  I  have  been  endeav- 
oring to  enforce.  If  our  minds  are  incapable  of 
comprehending  the  plan,  who  could  have  been  equal 
to  the  design  ?  "  Whence,  then,  cometh  wisdom, 
and  where  is  the  place  of  understanding,  seeing  it 
is  hid  from  the  eyes  of  all  living,  and  kept  close 
fromthefowlsof  the  air?  "^  ^  ^  God  understandeth 
the  way  thereof,  and  he  knoweth  the  place  thereof. 
For  he  looketh  to  the  ends  of  the  earth,  and  seeth 
under  the  whole  heaven,  to  make  the  weight  for 
the  winds     ^     *     -^     and  a  way  for  the  lightning  of 


68  MARKS  OF  DESIGN. 

the  thunder.  Then  did  he  see  it  and  declare  it; 
he  prepared  it,  yea,  and  searched  it  out.  And 
unto  man  he  said,  Behold  the  fear  of  the  Lord, 
that  is  wisdom,  and  to  depart  from  evil  is  under- 
standing," 


CHAPTER  III. 

TESTIMONY    OF  OXYGEN. 

Were  we  to  limit  our  regards  to  those  physical 
qualities  of  the  atmosphere  which  we  studied  in  the 
first  two  chapters,  we  should  overlook  the  most  won- 
derful adaptations  in  its  divine  economy.  These 
properties  belong  to  the  atmosphere,  in  great  meas- 
ure at  least,  in  virtue  of  its  aeriform  condition,  and, 
so  far  as  we  know,  an  atmosphere  composed  of 
other  gases,  and  still  having  the  same  density,  would 
soften  the  intensity  of  the  light,  and  diffuse  the 
genial  influences  of  the  sun's  heat,  as  well  as  air. 
Not  so,  however,  with  the  chemical  qualities  of  the 
atmosphere,  which  we  are  next  to  consider.  These 
belong  to  the  atmosphere  solely  as  air,  and  could  not 
have  been  obtained  with  any  other  known  materials. 

When  a  chemist  wishes  to  investigate  the  nature 
of  a  new  substance,  his  first  step  is  to  analyze  it. 
Let  us,  therefore,  as  a  preliminary  to  our  present  in- 
quiry, ascertain  what  is  the  composition  of  this 
aeriform  matter  we  call  air.  The  air  has  been  ana- 
lyzed hundreds  of  times  in  every  latitude  and  in 
every  climate  ;  and  the  result  has  been  uniformly 
that  which  is  given  in  the  following  table : — 

69 


70  COMPOSITION   OF  THE  ATMOSPHERE. 


Composition  of  the  Atmosphere, 


* 


Oxygen 20.61 

Nitrogen 77.95 

Carbonic  Dioxide 04 

Aqueous  Vapor  (average) 1.40 

Nitric  Acid,  \ 

Ammonia,  r   traces. 

Carburetted  Hydrogen,  )  

100.00 

Composition  in  Tons. 

Oxygen 1,233,010  billions  of  tons. 

Nitrogen 3,994,593       '*  " 

Carbonic  Dioxide 5,287       "  " 

Aqueous  Vapor 54,460       "  " 

Besides  oxygen  and  nitrogen  gases,  which,  as  you 
will  notice,  are  the  chief  constituents,  there  are  al- 
ways present  in  the  atmosphere  the  vapor  of  water, 
carbonic  dioxide,  and  ammonia  gas ;  and  if  we  add 
to  these  uniform  constituents  the  various  exhalations 
constantly  arising  from  the  earth,  we  shall  have  as 
accurate  an  idea  of  the  composition  of  the  air  as 
chemistry  can  give.  While,  however,  the  propor- 
tions of  oxygen  and  nitrogen  are  almost  absolutely 
constant,  those  of  the  other  ingredients  are  very 
fluctuating,  and  the  total  quantity  exceedingly  small, 
never  amounting  in  all,  exclusive  of  aqueous  vapor, 
to  more  than  one  part  in  a  thousand,  unless  in  some 
confined  locality,  and  under  very  unusual  circum- 

*  Miller's  Elements  of  Chemistry. 


THE  ATMOSPHERE  A   MIXTURE.  /I 

stances.  Do  not,  however,  measure  the  importance 
of  these  variable,  and  in  a  degree  accidental,  constit- 
uents by  their  amount,  for,  although  present  in  such 
small  quantities,  they  are  not  less  essential  in  the 
atmosphere  than  the  two  gases  which  make  up  al- 
most its  entire  mass. 

Moreover,  we  must  carefully  avoid  the  error  of 
considering  air  as  a  distinct  substance,  like  water 
or  coal.  On  the  contrary,  it  is  merely  a  mechanical 
mixture  of  its  constituent  gases,  and  is  in  no  sense 
a  definite  chemical  compound.  Indeed,  we  may 
regard  the  globe  as  surrounded  by  at  least  three 
separate  atmospheres, — one  of  oxygen,  one  of  nitro- 
gen, and  one  of  aqueous  vapor, — all  existing  simul- 
taneously in  the  same  space,  yet  each  entirely  dis- 
tinct from  the  other  two,  and  only  very  slightly 
influenced  by  their  presence.  To  each  of  these 
atmospheres  the  Author  of  nature  has  assigned 
separate  and  different  functions.  They  are  like  so 
many  servants  in  a  household,  each  with  a  distinct 
set  of  duties,  which  are  discharged  with  a  fidelity 
and  diligence  unknown  to  any  earthly  service.  Let 
us  consider  what  those  duties  are,  and  see  how 
skilfully  each  is  adapted  to  the  offices  which  it  is 
designed  to  fill. 

Were  all  the  other  constituents  of  the  air  re- 
moved, the  earth  would  still  be  surrounded  by  an 
atmosphere  of  oxygen,  having  about  one-fifth  of 
the  density,  and  exerting  at  the  surface  of  the 
globe  about  one-fifth  of  the  pressure,  of  the  pres- 
ent atmosphere.  In  studying  the  chemical  rela- 
tions of  air,  let  us  begin  with  some  of  the  more 


72  PERMANENT  AERIFORM   CONDITION. 

important  functions  of  this  remarkable  substance, 
and  these  will  fully  occupy  us  during  this  and  the 
succeeding  chapter. 

It  is  easy  to  prepare  oxygen  in  a  pure  state.  It 
is  then  a  perfectly  colorless  and  transparent  gas, 
and  so  persistently  does  it  retain  its  aeriform  con- 
dition that  it  cannot  be  reduced  to  the  liquid  state 
by  pressure  alone.  A  German  chemist,  Natterer, 
submitted  this  gas  to  a  pressure  of  over  forty-five 
thousand  pounds,  or  twenty  tons  on  a  square  inch, 
but  he  did  not  succeed  in  changing  its  condition. 
More  recently,  by  the  combined  action  of  great 
pressure  and  the  most  intense  cold  which  can  be 
artificially  produced,  all  the  gases  formerly  called 
permanent  have  been  liquefied,  and  oxygen  among 
the  number.  But  this  remarkable  result,  while  it 
shows  conclusively  that  the  so-called  permanent 
gases  differed  from  other  forms  of  aeriform  matter 
in  degree  only,  and  not  in  kind,  also  brings  into 
prominence  the  extreme  qualities  of  these  constitu- 
ents of  our  atmosphere.  Most  aeriform  substances 
may  be  reduced  to  liquids  by  pressure  under  a  very 
moderate  reduction   of  temperature  ;"^  but  oxygen 

*  For  every  aeriform  substance  there  is  a  fixed  temperature  above 
which  the  gas  cannot  be  reduced  to  a  liquid"  by  any  pressure,  how- 
ever great ;  but  below  which  this  change  can  be  produced  if  the 
mechanical  force  is  sufficient.  This  fixed  temperature  is  called  **  the 
critical  point,"  and  the  pressure  required  to  condense  a  gas  becomes 
less  and  less  as  the  temperature  is  reduced  below  this  point,  which 
differs  very  greatly  with  different  substances.  The  critical  point  of 
many  of  the  known  gases  is  above  the  ordinary  temperature  of  the  air, 
and  a,U  such  gases  may  be  reduced  to  liquids  simply  by  mechanical 


PERMANENT  AERIFORM   CONDITION.  73 

and  nitrogen  retain  their  aeriform  condition  under 
the  widest  variations  of  temperature  which  exist 
on  the  earth. 

The  importance  of  this  fact  will  be  seen  at  once 
on  comparing  the  condition  of  the  oxygen  and 
nitrogeiTm The  atmosphere  with  that  of  the  aqueous 
vapor.  A  fall  of  temperature  of  only  a  few  degrees 
will  generally  condense  a  portion  of  the  vapor,  and, 
small  as  is  its  relative  amount,  the  resulting  rain  is 
at  times  poured  down  upon  the  earth  in  deluging 
floods ;  and  if  you  consider  what  must  have  been 
the  destructive  results  had  the  whole  mass  of  the 
atmosphere  been  liable  to  a  similar  fluctuation,  even 
under  extreme  conditions,  you  will  discover  in  the 
permanency  of  oxygen  a  most  obvious  adaptation 
of  its  properties  to  the  thermal  condition  of  our 
globe. 

The  permanently  aeriform  state  of  oxygen  will 
appear  still  more  remarkable  when  we  consider  how 
largely  it  enters  into  the  composition  of  the  solid 
crust  of  the  earth.     Oxygen  belongs  to  that  class 

pressure.  The  critical  point  of  carbonic  dioxide  gas  is  about  88°,  and 
as  this  temperature  is  within  the  limits  of  the  variations  in  our  cli- 
mate, carbonic  dioxide  furnishes  the  most  convenient  illustration  of 
the  principle  we  are  discussing.  For  example,  in  some  specimens  of 
granite  rock  we  find  cavities  which  are  filled  with  liquid  carbonic  di- 
oxide if  the  temperature  is  below  87° — as  can  readily  be  seen  by  ex- 
amining with  a  microscope  the  thin  sections  prepared  for  this  purpose 
— but  when  the  temperature  rises  above  87°  the  liquid  at  once  disap- 
pears, to  condense  again,  however,  as  soon  as  the  temperature  falls. 
The  critical  points  of  oxygen  and  nitrogen  are  not  exactly  known, 
but  must  be  more  than  150®  below  the  zero  of  Fahrenheit,  and  hence 
chemists  did  not  succeed  in  condensing  these  gases  to  liquids  until 
they  submitted  them  to  extreme  cold  as  well  as  to  great  pressure. 
4 


74  PERMANENT  AERIFORM   CONDITION. 

of  substances  which  the  chemists  call  elements, 
because  they  have  never  succeeded  in  resolving 
them  into  simpler  parts,  and  of  all  the  elements 
it  is  by  far  the  most  widely  diffused.  As  we  have 
already  seen,  one-fifth  of  the  volume  of  the  atmos- 
phere consists  of  this  gas  ;  but  this  is  a  small  amount 
compared  with  that  which  enters  into  the  com- 
position of  most  substances.  You  may  be  surprised 
at  the  statement,  but  it  is  nevertheless  true,  that 
between  one-half  and  one-third  of  the  crust  of  this 
globe  and  of  the  bodies  of  its  inhabitants  consists 
of  oxygen.  No  less  than  eight-ninths  of  all  water  is 
formed  of  the  same  gas.  It  makes  up  three-fourths 
of  our  own  bodies,  not  less  than  four-fifths  of  every 
plant,  and  at  least  one-half  of  the  solid  rocks.  Re- 
membering now  that  twenty  tons  of  pressure  on  a 
square  inch  are  not  sufficient  to  reduce  oxygen  to  a 
liquid  condition,  consider  what  must  be  the  strength 
of  that  force  which  holds  it  thus  imprisoned.  In  a 
tumbler  of  water  there  are  no  less  than  six  cubic 
feet  of  oxygen  gas,  condensed  to  a  liquid  condi- 
tion, and  held  there  by  the  continuous  action  of 
a  force  which  can  be  measured  only  by  hundreds  of 
tons  of  pressure.  We  call  the  force  chemical  af- 
finity; but  who  shall  measure  its  power?  Who  but 
He  who  could  make  with  such  a  subtile  material 
the  rocks,  with  which  he  "  laid  the  foundations  of 
the  earth,"  and  the  waters  which  roll  over  its  sur- 
face? 

Oxygen  gas,  like  all  other  forms  of  aeriform 
matter,  tends  to  expand,  and  can  be  prevented 
from   obeying  this   natural  tendency  only   by   en- 


DENSITY   OF  OXYGEN.  75 

closing  it  in  an  air-tight  receiver.  As  it  exists  in 
our  glass  jars,  under  the  ordinary  conditions  of 
temperature  and  pressure,  one  cubic  foot  of  oxy- 
gen weighs  590.8  grains,  although  in  its  more  ex- 
panded state,  as  it  exists  in  the  atmosphere  at  the 
surface  of  the  globe,  it  has  but  one-fifth  of  this 
density.  One  cubic  foot  of  nitrogen  gas  weighs, 
under  the  same  circumstances,  517.5  grains;  but 
although  there  is  such  a  decided  difference  between 
the  specific  gravities  of  the  two  gases,  yet  so  per- 
fectly are  they  mixed  together  throughout  the  whole 
extent  of  the  atmosphere,  that  analysis  has  been  un- 
able to  detect  more  than  a  very  slight  difference  in 
composition  between  the  air  brought  from  the  sum- 
mits of  the  Alps  and  that  from  the  deepest  mine 
in  Cornwall.  Why,  you  may  ask,  do  not  these  gases 
obey  the  well-known  laws  of  hydrostatics,  the  heav- 
ier oxygen  sinking  to  the  surface  of  the  earth,  and 
the  lighter  nitrogen  floating  above  it  ?  Simply 
because  gases,  unlike  the  other  forms  of  matter, 
have  the  property  of  '*  diffusing  "  through  each  other, 
and  existing  together  in  the  same  space.  The  pres- 
ence of  one  gas  does  not  prevent  the  entrance  of 
another  into  the  space  which  it  occupies,  and  if  two 
open  jars,  containing  different  gases,  are  placed 
together,  mouth  to  mouth,  each  gas  will  expand 
until  it  fills  the  whole  volume  of  both  receivers. 
Moreover,  the  greater  the  difference  between  the 
densities  of  the  gases,  and  the  greater  consequent 
disposition  to  separate,  the  stronger  is  their  ten- 
dency to  mix  together.  This  process  is  known  as 
"  diffusion,"  and  plays  a  very  important  part  in  the 


^6  DIFFUSION. 


plan  of  creation.  Were  no  such  law  in  operation  the 
two  gases  composing  air  would  have  separated  par- 
tially, and  the  atmosphere  have  become  unfitted  for 
many  of  its  important  functions.  Take,  for  example, 
the  function  of  transmitting  sound. 

As  the  air  is  now  constituted,  there  is  a  constancy 
of  pitch,  however  far  sound  travels.  Any  tone  once 
generated  remains  the  same  tone  until  it  dies  away. 
Its  degree  of  loudness  alters  in  proportion  to  the 
distance  of  the  listener,  but  the  pitch  is  constant. 
Were  it  not,  however,  for  this  law  of  diffusion, — 
were  the  atmosphere  not  perfectly  homogeneous, 
and  the  gases  of  which  it  consists  even  partially 
separated, — there  would  have  been  a  very  different 
result.  The  constancy  of  pitch  could  no  longer 
have  been  depended  upon.  The  sound  as  it  travelled 
would  vary  its  pitch  with  the  ever-varying  medium 
through  which  it  passed,  and  would  arrive  at  the  ear 
with  a  tone  entirely  different  from  that  with  which 
it  started.  Nor  would  it  require  any  great  differ- 
ence in  the  medium  to  produce  a  sensible  result  and 
to  confuse  all  those  delicate  differences  of  pitch  on 
which  the  whole  art  of  music  depends.  Whenever, 
therefore,  you  may  be  next  enjoying  the  grand  Pas- 
toral Symphony  of  Beethoven  or  the  Requiem  of 
Mozart,  recall  the  careful  adjustment  of  forces  by 
which  alone  these  magnificent  creations  of  genius 
were  rendered  possible,  and  you  cannot  fail  to  re- 
cognize in  this  simple  law  of  nature  the  same  hand 
that  first  strung  the  lyre  and  made  the  soul  of  man 
responsive  to  its  seven  notes. 

Returning  again  to  the  qualities  of  oxygen,  let  us 


PASSIVE  AND   ACTIVE   CONDITION.  JJ 

notice,  in  the  next  place,  that  it  is  entirely  destitute 
either  of  odor  or  of  taste.  This  fact  is  a  matter  of 
common  experience  ;  for  as  oxygen  exists  in  a  free 
state  in  the  atmosphere,  it  would  there  manifest 
these  properties  did  they  exist :  and  reflect  how 
essential  these  negative  qualities  are  to  our  comfort 
and  well-being.  Moreover,  in  its  ordinary  con- 
dition, oxygen  seems  entirely  devoid  of  any  active 
properties.  It  does  not  affect  the  most  delicatg  and 
evanescent  vegetable  dyes,  which  the  weakest  chem- 
ical agents  will  either  alter  or  destroy.  And  con- 
sider the  oxygen  as  it  exists  in  the  air.  How  bland 
and  seemingly  inactive  it  is  there  ?  Reflect  that  it 
bathes  the  most  delicate  animal  organisms,  that  it 
pervades  the  minutest  air-passages  of  the  lungs, — 
remember  that  it  is  in  contact  with  all  matter, — 
and  every  substance  will  seem  to  bear  evidence  to 
the  fact  that  oxygen  in  the  state  of  gas  possesses  no 
active  properties,  and  is  incapable  of  manifesting 
any  strong  chemical  force.  And  yet,  if  you  infer 
that  oxygen  always  appears  in  the  passive  con- 
dition, and  is  under  all  circumstances  incapable  of 
violent  action,  you  will  be  entirely  deceived ;  for  so 
far  from  being  one  of  the  weakest,  it  is  the  strong- 
est of  the  chemical  elements,  and  beneath  this 
apparent  mildness  there  is  concealed  an  energy  so 
violent,  that,  when  once  thoroughly  aroused,  noth- 
ing can  withstand  it.  A  single  spark  of  fire  will 
change  the  whole  character  of  this  element,  and 
what  was  before  inert  and  passive  becomes  in  an 
instant  violent  and  irrepressible.  The  gentle  breeze 
which  was  waving  the  corn  and  fanning  the  brows- 


78  NATURE   OF  FIRE. 

ing  herds,  becomes  the  next  moment  a  consuming 
fire,  before  which  the  works  of  man  melt  away  into 
air. 

And  here  I  must  correct  an  erroneous,  although 
very  common  impression,  that  there  is  something 
substantial  in  fire.  This  is  one  of  those  ideas,  origi- 
nating in  an  illusion  of  the  senses,  which  we  have 
inherited  from  a  more  ignorant  age,  and  which  our 
modern  science  cannot  wholly  dispel  from  the  popu- 
lar mind.  Fire  was  formerly  regarded  as  one  of  the 
elementary  forms  of  matter,  and  all  burning  was 
supposed  to  consist  in  the  escape  of  this  principle  of 
fire,  previously  pent  up  in  the  combustible  substance. 
In  support  of  this  doctrine  the  old  philosophers  con- 
fidently pointed  at  flame  as  the  visible  manifestation 
of  the  escaping  fire-element ;  and,  childish  as  this 
doctrine  may  seem,  it  was  the  prevalent  belief  of  the 
world  for  at  least  two  thousand  years. 

The  last  phase  which  this  doctrine  assumed  was 
the  phlogiston  theory  of  the  last  century.  In  the 
hands  of  Bergmann  and  Stahl,  the  vague  ideas  of 
the  time  received  a  more  material  form,  and  were 
embodied  in  a  philosophical  system.  They  termed 
the  principle  of  fire  phlogiston,  and  burning,  or  the 
escape  of  fire,  dephlogistication,  and  their  ingenious 
system  did  not  a  little  to  retard  the  progress  of 
truth.  The  philosophers  of  that  age  either  took  no 
account  of  the  increase  of  weight  which  results  from 
burning,  or  attempted  to  explain  the  few  instances 
in  which  the  fact  was  forced  upon  their  attention  by 
the  fanciful  notion  of  Aristotle — that  the  essence  of 
fire  was  specifically  light.     Hence,  they  reasoned, 


THEORY   OF  PHLOGISTON.  79 

phlogiston  buoys  up  all  bodies  into  which  it  enters, 
and  after  its  escape  in  the  process  of  burning,  the 
burnt  material  must  weigh  more  than  before.  It 
was  not  until  1783  that  the  true  theory  of  combus- 
tion was  discovered,  and  from  this  discovery  mod- 
ern chemistry  dates.  The  fortunate  discoverer  was 
Lavoisier.  He  proved,  by  simply  weighing  the  prod- 
lucts  of  combustion,  that  burning,  instead  of  being 
a  loss  of  phlogiston,  is  a  union  of  the  burning  sub- 
stance with  the  oxygen  of  the  air,  and  this  theory 
is  now  one  of  the  best  established  principles  of 
science. 

Burning  is  merely  chemical  change,  and  all  com- 
bustion with  which  we  are  familiar  in  common  life 
is  a  chemical  combination  of  the  burning  substance, 
whether  it  be  coal,  wood,  oil,  or  gas,  with  the  oxygen 
of  the  air.  Combustion  is  simply  a  process  of  chem- 
ical combination,  and  the  light  and  heat  which  are 
evolved  in  the  process  are  only  the  concomitants  of 
the  chemical  change.  Why  those  mysterious  in- 
fluences of  light  and  heat  are  radiated  from  the  coal 
which  is  combining  with  oxygen  in  our  grates,  we 
may  understand  better  hereafter  ;  but  this  much  we 
already  know, — the  sensations  of  light  and  heat  are 
caused  by  waves  of  an  ethereal  medium  breaking 
upon  the  extremities  of  the  delicate  nerves  of  our 
human  organism ;  and  such  waves  are  set  in  motion 
during  the  chemical  change  which  we  call  combus- 
tion. What  the  chemist  mostly  studies,  however,  is 
the  change  itself,  and  to  this  we  will  for  the  present 
confine  our  attention. 

The  chief  products  of  ordinary  combustion,  that  is, 


80  WEIGHT   OF  THE   SMOKE. 

the  compounds  of  oxygen  with  the  elements  of  coal, 
wood,  and  illuminating  gas,  are  only  two  in  number, 
carbonjc  dioxide  ^as  and  aqueous  vapor.  These 
products,  as  is  well  known,  are  perfectly  colorless  and 
transparent  aeriform  substances,  wholly  without  odor 
or  taste,  and  entirely  devoid  of  every  active  quality. 
For  this  reason  they  escape  without  observation  from 
the  burning  wood,  ascend  our  chimneys,  and  by  the 
force  of  diffusion  are  spread  throughout  the  atmos- 
phere ;  but  if,  as  may  readily  be  done  by  chemical 
means,  we  collect  the  neglected  smoke  and  weigh 
it,  we  shall  find  that  it  weighs  much  more  than  the 
burnt  wood,  and,  as  more  careful  experiments  will 
show,  its  weight  is  exactly  equal  to  that  of  the  wood 
added  to  that  of  the  oxygen  of  the  air  consumed 
during  the  burning. 

Moreover,  this  smoke,  though  so  long  unno- 
ticed by  man,  was  not  overlooked  by  the  Author 
of  nature.  It  is  a  part  of  his  grand  and  benefi- 
cent design  in  the  scheme  of  organic  nature.  No 
sooner  do  the  products  of  that  wood  burning  on 
the  hearth  escape  into  the  free  expanse  of  the  outer 
air,  than  a  new  cycle  of  changes  begins.  The  car- 
bonic dioxide  and  the  aqueous  vapor,  after  roving 
at  liberty  for  a  time,  are  absorbed_by  the  leaves  of 
some  jwide-spreading  tree,  smiling  in  the  sunshine, 
andln  the  tiny  laboratory  of  their  green  cells  are 
worked  up  by  those  wonderful  agents,  the  sun-rays, 
into  new  wood,  absorbing  from  the  sun  afresh  supply 
of  power,  which  is  destined,  perhaps,  to  shed  warmth 
and  light  around  the  fireside  of  a  future  generation. 

But  let  us  not  anticipate  our  subject.     In  a  future 


FIRE,   HOW   SUSTAINED.  8 1 

chapter  we  shall  discuss  this  wonderful  cycle  of 
changes  at  some  length.  At  present  I  wish  to 
direct  your  attention  to  the  remarkable  contrast 
of  qualities  presented  by  the  element  oxygen  in  its 
active  and  passive  conditions.  How  is  this  com- 
plete inversion  of  properties  to  be  explained  ? 
There  is  a  cloud  of  mystery  hanging  over  the  sub- 
ject, which  the  progress  of  knowledge  has  not  as  yet 
entirely  dispelled  ;"^  but,  so  far  as  the  cause  is  known, 
I  will  endeavor  to  make  it  intelligible.  The  difference 
in  the  action  of  oxygen  in  these  two  conditions  de- 
pends on  temperature.  At  the  ordinary  tempera- 
ture of  the  air  its  chemical  affinities  are  dormant, 
and,  although  endowed  with  forces  which  are  irre- 
sistible when  in  action,  it  awaits  the  necessary  con- 
ditions to  call  them  forth.  One  of  the  grandest 
works  of  ancient  art  which  have  come  down  to  us  is 
the  colossal  statue  of  the  Farnese  Hercules.  The 
hero  of  ancient  mythology  is  represented  in  an  erect 
form,  leaning  on  his  club,  and  ready  for  action ;  but 
for  the  moment  every  one  of  the  well-developed 
muscles  of  his  ponderous  frame  is  fully  relaxed,  and 
the  figure  is  a  perfect  ideal  of  repose,  yet  a  wonder- 
ful embodiment  of  power.  Here  in  this  antique  we 
have  most  perfectly  typified  the  passive  condition 
of  oxygen,  the  hero  of  the  chemical  elements.  Raise 
now  the  temperature  to  a  red  heat,  and  in  a  moment 
all  is  changed.     The  dormant  energies  of  its  mighty 

■^During  the  past  four  years  the  study  of  thermo-chemistry  has 
given  us  the  first  clue  toward  a  solution  of  this  problem  ;  but  as  yet 
the  results  do  not  admit  of  a  concise  and  popular  statement. 

4* 


A 


S2  FIRE,   HOW   SUSTAINED. 

powers  are  aroused,  and  it  rashes  into  combination 
with  all  combustible  matter,  surrounded  by  those 
glorious  manifestations  of  light  and  heat  which  every 
conflagration  presents. 

In  order  to  evoke  the  latent  forces  in  the  oxygen 
of  the  atmosphere,  it  is  not  necessary,  however,  to 
raise  the  temperature  of  any  considerable  portion 
either  of  the  gas  or  of  the  combustible.  There  is 
a  provision  in  nature  by  which  chemical  combina- 
tion, once  started  at  any  portion  of  the  combustible 
mass,  is  sustained  until  the  whole  is  consumed.  (All 
chemical  combination  is  attended  by  the  evolution 
^  of  heaty  and  in  the  combination  of  oxygen  with 
most  combustible  substances  the  amount  of  heat 
thus  generated  is  so  great,  that  by  the  burning  of 
one  portion  sufficient  heat  is  evolved  to  raise  the 
temperature  of  a  second  portion  to  the  point  of 
ignition,  and  thus  the  process  is  continued.  Con- 
sider, for  example,  what  takes  place  in  the  burning 
of  a  jet  of  gas.  We  start  the  combustion  by  bringing 
the  flame  of  a  lighted  match  over  the  orifice  of  the 
burner.  By  this  the  temperature  of  the  gas  and 
that  of  the  air  surrounding  it  are  raised  to  a  red- 
heat,  and  chemical  combination  at  once  ensues. 
But  the  chemical  union,  as  just  stated,  is  attended 
with  the  evolution  of  great  heat,  which,  before  it  is 
dissipated,  raises  to  the  point  of  ignition  the  tem- 
perature of  the  next  portion  of  gas  issuing  from 
the  burner.  This,  combining  in  its  turn  with  oxy- 
gen, generates  a  fresh  quantity  of  heat,  and  thus 
keeps  up  the  combustion  so  long  as  the  gas  is  sup- 
plied.    What  I   have   shown   to   be  true  of  a  gas- 


POINT   OF   IGNITION.  83 

burner  is  equally  true  of  all  ordinary  combustion, 
and  so  a  single  spark  may  be  sufficient  to  light  up  a 
conflagration  which  will  reduce  to  ashes  a  whole 
village  or  involve  a  city  in  ruin. 

Thus  it  appears  that  burning  is  chemical  combi- 
nation with  oxygen,  that  this  union  is  attended  with 
the  evolution  of  heat,  and  that  a  high  temperature 
is  the  condition  under  which  oxygen  manifests  its 
latent  power.  But,  you  may  say,  these  facts  do  not 
explain  the  difference  between  the  two  states  of 
oxygen,  they  merely  give  the  conditions  under  which 
these  states  are  manifested  ;  and  this  is  true.  Why 
it  is  that  at  one  temperature  oxygen  is  so  completely 
passive,  and  at  another  temperature,  a  few  hundred 
degrees  higher,  so  highly  active,  we  cannot  fully  ex- 
plain ;   but  the  facts  are  undisputed. 

The  temperature  at  which  oxygen  assumes  its 
active  condition  is  called  the  point  of  ignition.  Al- 
though fixed  for  each  substance,  it  differs  very 
greatly  with  the  different  kinds  of  combustible  mat- 
ter, being  determined,  apparently,  by  their  relative 
affinities  for  the  great  fire-element.  Thus  phos- 
phorus ignites  at  a  temperature  less  than  that  of 
boiling  water,  sulphur  at  about  500*^,  wood  only  at  a 
full  red-heat,  anthracite  coal  at  a  white-heat,  while 
iron  requires  the  highest  heat  of  a  blacksmith's  forge. 
Beginning  with  a  phosphorus  match,  which  can  be 
ignited  by  friction,  and  using  the  more  combustible 
materials  as  kindlings,  we  can  readily  attain  in  our 
furnaces  the  highest  temperature  required,  and  thus 
the  energies  of  this  powerful  agent  are  fully  at  the 
command  of   man.     But  notice   at  the  same  time 


84  FIR       HOW   RESTRAINED. 

that  the^  point  of  ignition  of  wood,  coal,  and  com- 
mon combustibles,  has  been  placed  sufficiently  above 
the  ordinary  temperature  of  the  air  to  insure  the 
general  safety  of  our  combustible  dwellings ;  and 
when  we  consider  how  liable  they  are,  even  now,  to 
accidents  from  fire,  we  shall  appreciate  the  care 
which  has  been  taken  by  our  Heavenly  Father  to 
guard  us  against  this  terrible  danger. 

But  even  this  precaution  would  have  been  insuf- 
ficient to  secure  safety,  were  it  not  that  the  active 
energies  of  oxygen,  even  when  aroused,  have  been 
most  carefully  tempered  by  extreme  dilution.  It 
would  be  easy  to  show  by  experiment  that  the 
slowness  of  combustion  depends  on  the  fact  that  in 
the  atmosphere  oxygen  is  mixed  with  a  great  mass 
of  an  inert  gas,  and  the  proportions  have  been  so 
adjusted  in  the  scheme  of  creation  as  generally  to 
restrain  the  awakened  energies  of  the  fire-element 
within  the  narrow  limits  which  man  appoints  ;  but 
when,  through  his  misfortune  or  carelessness,  it  over- 
rides these  limits,  and,  from  administering  to  man's 
wants,  becomes  the  agent  of  his  destruction,  we  are 
reminded  in  the  awful  conflagration  by  what  a  deli- 
cate tenure  we  hold  our  earthly  possessions,  and 
how  small  a  change  would  be  sufficient  to  involve 
all  organized  matter  in  a  general  conflagration. 
Remember  now  that  fire  is  one  of  the  most  valuable 
servants  of  mankind  ;  that  it  is  the  source  of  all 
artificial  heat  and  light ;  that  in  the  steam-engine  it 
is  the  apparent  origin  of  that  power  which  animates 
the  commerce  and  the  industry  of  the  civilized 
world  ;  that  under  its  influence  iron  becomes  plastic, 


FIRE,   HOW   RESTRAINED.  85 

and  the  ores  give  up  their  metallic  treasures ;  that 
it  is,  in  fine,  the  agent  of  all  the  arts, — and  you  can- 
not wonder  that  in  a  ruder  age  the  Romans  should 
have  enthroned  its  presiding  deity  on  Olympus,  or 
the  Persians  worshipped  its  supposed  essence  as 
divinity  itself.  Looking  at  it  again,  in  the  light  of 
modern  science,  as  merely  the  manifestation  of  the 
latent  power  of  this  bland  and  diffusive  atmosphere, 
the  truth  seems  almost  incredible.  To  think  that 
this,  the  strongest  of  the  chemical  elements, — which, 
although  a  permanent  gas,  forms  more  than  one-half 
of  the  solid  crust  of  the  earth,  and  is  endowed  with 
such  mighty  af^nities  that  it  is  retained  securely  in 
this  solid  state, — could  have  been  so  shorn  of  its  en- 
ergies as  not  to  singe  the  down  of  the  gossamer,  and 
yet  so  tempered  that  its  powers  may  be  evoked  at 
the  will  of  man  and  made  subservient  to  his  wants  ! 
To  me  the  double  condition  of  oxygen  is  one  of  the 
most  remarkable  phenomena  of  nature.  I  ponder 
it  again  and  again,  with  increasing  wonder  and  ad- 
miration at  the  skill  of  the  infinite  Designer,  who  i 
has-been  able  to  unite  in  the  same  element  perfect 
mildness  and  immeasurable  power.  It  seems  as  if 
the  millennium  of  the  Hebrew  prophet  were  pre- 
figured in  the  atmosphere.  "  The  wolf  also  shall 
dwell  with  the  lamb,  and  the  leopard  shall  lie  down 
with  the  kid,  and  the  calf  and  the  young  lion  and 
the  fatling  together,  and  a  little  child  shall  lead 
them.'' 

If  I  have  succeeded  in  making  clear  the  relations 
of  this  twofold  character  of  oxygen  to  man  and  his 
works,  I  think  that  you  cannot  fail  to  have  been 


86  OXYGEN   THE  WORLD-BUILDER. 

impressed  with  the  evidence  of  design  which  the 
subject  affords.  This  evidence  is  seen  in  the  facts, 
first,  that  the  same  element  is  at  different  tempera- 
tures endowed  with  such  opposite  and  apparently 
incompatible  qualities  ;  secondly,  that  in  each  of  its 
conditions  the  properties  are  so  skilfully  adapted 
to  the  functions  which  it  is  appointed  to  perform  ; 
thirdly,  that  the  temperature  at  which  it  assumes 
its  active  state  has  been  so  accurately  adjusted  to 
the  thermal  conditions  of  the  globe ;  and  lastly, 
that  its  active  energies  have  been  so  carefully 
guarded,  and  placed  to  so  great  a  degree  under  the 
control  of  man.  But  we  have  not  as  yet  one-half 
exhausted  the  subject.  Here,  as  everywhere  else 
in  nature,  the  argument  is  cumulative;  the  more 
we  study,  and  the  more  our  knowledge  is  enlarged, 
the  more  it  grows  upon  us ;  and  wherever  we  may 
leave  the  field,  we  always  are  conscious  that  there 
is  a  still  richer  harvest  to  be  reaped  beyond. 

If  the  crust  of  the  globe  is  a  fair  sample  of  the 
whole  mass,  oxygen  was  the  chief  material  employed 
by  the  Great  Architect  in  constructing  our  earth. 
Moreover,  world-building  was  a  process  of  burning, 
like  those  we  have  been  studying,  and  the  founda- 
tions of  the  earth  were  undoubtedly  laid  in  flames. 

When  we  attempt  to  break  up  the  various  ma- 
terials around  us  into  simpler  parts,  we  soon  reach 
a  class  of  substances  which  cannot  be  further  de- 
composed. Simple  inspection  will  show  that  gran- 
ite rock,  for  example,  is  a  mixture  of  three  min- 
erals, called  feldspar,  mica,  and  quartz.     We  know, 


OXYGEN   THE   WORLD-BUILDER.  8/ 

also,  that  feldspar  consists  of  alumina,  potash,  and 
silica,  that  mica  contains  the  same  materials  in 
different  proportions,  and  that  quartz  is  silica  alone. 
Lastly,  the  chemists  have  discovered  that  alumina 
is  composed  of  aluntiniun  and  oxygen^  potash  of  po- 
tassium  and  oxygen,  and  silica  of  silicon  and  oxygen. 
But  here  we  must  stop  ;  for  when  you  ask  us  of 
what  these  last-named  materials  are  made,  we  find 
ourselves  in  the  condition  of  the  old  philosopher, 
who  got  on  very  well  with  his  flat  earth,  support- 
ing it  on  an  elephant,  and  the  elephant  on  a  tor- 
toise, until  he  came  to  seek  a  resting-place  for  the 
tortoise ;  but  then  his  theory  failed.  So  is  it  with 
our  science.  These  undecomposed  materials  are 
the  blocks  on  which  the  whole  is  built ;  and  we  are 
totally  ignorant  of  what  lies  below. 

We  call  all  substances  which  have  never  yet 
been  decomposed,  whatever  may  be  their  nature, 
chemical  elements,  and  of  such  some  seventy  are  now 
known.  Setting  apart  oxygen  as  the  supporter  of 
combustion,  the  great  mass  of  the  remaining  ele- 
ments are  combustible  ;  that  is,  under  certain  con- 
ditions they  combine  rapidly  with  oxygen,  evolv- 
ing light  and  heat.  Indeed,  many  of  the  combus- 
tible substances  with  which  we  are  most  familiar 
are  elements.  Charcoal  is  an  element,  phosphorus 
is  an  element,  sulphur  is  an  element,  iron  and  all 
other  metals  are  elements,  and  out  of  such  com- 
bustible materials,  together  with  oxygen,  the  world 
is  made,  but  chiefly  out  of  oxygen. 

When  we  burn  charcoal  in  air,  or  in  pure  oxygen 
gas,  the  burning  is  a  process  of  world-making.     The 


88  WORLD-BUILDING. 

charcoal  combines  with  oxygen,  and  the  result  is 
a  transparent,  colorless  gas,  called  carbonic  dioxide. 
Many  may  not  have  heard  of  such  a  substance  be- 
fore, but  it  is  always  present  in  the  atmosphere,  at 
least  in  small  quantities,  and  if  we  continue  our 
process  of  world-making  a  little  further,  we  shall 
find  that  it  enters  into  the  composition  of  some  of 
the  most  familiar  rocks  and  minerals. 

I  have  at  the  bottom  of  this  closed  glass  tube  a 
small  piece  of  a  yellowish-white  metal,  looking  very 
much  like  a  flattened  shot ;  and  so  it  is,  but  the 
metal  is  not  lead,  although  it  resembles  lead  very 
closely.  Like  lead  it  is  quite  soft,  and  can  be  easily 
beaten  into  leaves  thinner  than  writing  paper ;  but 
it  is  very  much  lighter  than  lead,  and  tarnishes  so 
rapidly  in  the  air  that  we  are  obliged  to  keep  it  thus 
protected.  We  call  the  metal  calcium,  and  although 
you  may  never  have  seen  the  substance  before,  it  is 
one  of  the  most  abundant  metals  in  nature,  yet 
seldom  seen,  because  of  the  extreme  difficulty  with 
which  it  is  extracted  from  its  ores.  When  heated  to 
redness,  calcium  burns  with  a  brilliant  white  light 
and  a  scintillating  flame.  In  burning,  it  combines,  of 
course,  with  oxygen,  and  the  result  is  lime,  com- 
mon quick  lime,  such  as  is  used  for  making  mortar. 
This  is  a  process  which  in  the  original  world-mak- 
ing must  have  played  a  very  important  part,  for 
lime  rocks  form  a  large  portion  of  the  earth's  crust. 
None  of  these  rocks,  however,  will  slake  like  quick- 
lime, and  we  must  go  a  step  further  in  our  world-build- 
ing, and  bring  in  the  agency  of  water,  before  we  can 
reach  the  actual  condition  of  things. 


WORLD-BUILDING.  89 

We  have  now  before  us  two  products  of  burning, 
one  a  solid,  called  lime,  made  by  uniting  calcium 
with  oxygen,  the  other  a  gas,  called  carbonic 
dioxide,  made  by  uniting  charcoal  with  oxygen. 
Both  are  soluble  to  a  certain  extent  in  water,  and 
these  clear  solutions,  called  lime-water  and  soda- 
water  respectively,  are  even  more  familiar  to  you 
than  the  substances  themselves.  Mix  now  the  so- 
lutions together.  The  water  becomes  at  once  very 
turbid,  and  there  soon  settles  from  it  a  white  pow- 
der. The  lime  and  carbonic  dioxide  have  united, 
and  this  is  the  result.  If  we  collect  and  examine 
the  white  powder  we  shall  find  that  it  is  chalk,  and 
from  the  same  material,  spread  in  thick  layers  over 
the  ocean-bed,  and  subsequently  hardened  by  the 
mutual  action  of  heat  and  water,  have  been  formed 
limestone,  marble,  and  the  different  varieties  of  lime 
rock,  which  are  all  ores  of  calcium. 

But  we  may  study  with  profit  a  second  example 
of  world-building.  I  have  here  a  small  quantity  of 
another  very  abundant  element,  called  silicon,  but, 
like  calcium,  a  comparative  rarity,  because  it  is  with 
difficulty  obtained  pure.  It  resembles  in  many  re- 
spects carbon,  and  has  been  observed  in  three  dif- 
ferent states,  corresponding  to  charcoal,  graphite, 
and  diamond  Like  carbon,  it  also  is  combustible, 
combining  with  the  oxygen  of  the  air  when  heated 
to  a  high  temperature,  and  forming  a  very  hard 
white  solid,  called  by  chemists  silica,  which  is  the 
same  thing  as  quartz,  rock-crystal,  agate,  jasper, 
calcedony,  opal,  etc.  All  these  familiar  minerals  are 
merely  different  conditions  of  this  one  material,  and 


90  WORLD-BUILDING. 

contain  over  one-half  their  weight  of  oxygen  gas. 
When  ground  to  a  coarse  powder  by  the  action  of 
running  streams,  they  become  sand,  and  the  grains 
of  sand,  compacted  together,  form  sandstone  and 
similar  rocks ;  and  you  will  begin  to  appreciate  the 
enormous  amount  of  silicon  which  must  have  been 
burnt  up  in  the  process  of  world-making,  when  you 
learn  that  at  least  one-half  of  the  solid  crust  of  the 
earth  consists  of  silica  in  its  different  varieties. 

Setting  aside  the  silica  for  a  moment,  let  us 
turn  to  another  very  widely  distributed  element,^ 
called  aluminum.  This  brilliant  white  metal,  com- 
paring favorably  even  with  silver  in  lustre,  was,  until 
very  recently,  as  great  a  rarity  as  calcium  or  silicon  ; 
but  within  a  few  years  a  process  has  been  discovered 
by  which  it  can  be  extracted  from  its  ore  at  a  cost 
sufficiently  low  to  render  the  metal  available  in  the 
arts,  and  it  has  now  come  into  quite  general  use  for 
making  mathematical  instruments,  for  jewelry,  and 
for  similar  purposes.  It  forms  also,  with  copper,  a 
valuable  alloy,  which  does  not  readily  tarnish,  and 
resembles  gold  so  closely  that  the  two  cannot  be 
distinguished  by  their  external  appearance. 

Aluminum,  like  most  of  the  metals,  is  combusti- 
t)le,  although  it  does  not  burn  readily  in  the  air, 
unless  the  temperature  is  very  high  and  the  metal 
finely  subdivided ;  but  it  then  burns  very  brilliantly, 
emitting  a  vivid  light,  and  forming  a  compound 
called  by  chemists  alumina,  which  is  melted  by  the- 
intense  heat  to  a  yellowish  transparent  glass,  and  is 
the  same  substance  from  which  nature  makes  the 
sapphire  and  the  ruby,  Emery  also,  which,  on 
account  of  its  great  hardness,  is  used  so  largely  for 


WORLD-BUILDING.  9 1 

polishing,  is  only  a  rougher  form  of  the  same  ma- 
terial. Unite  now  the  alumina  to  silica,  add  water, 
and  we  get  clay.  Burn  the  clay,  and  we  have,  ac- 
cording to  the  fineness  of  the  materials,  porcelain, 
pottery-ware,  or  bricks. 

Taking  next  the  element  magnesium,  which  is  also 
a  brilliant  white  metal,  allied  to  zinc,  you  notice  that 
it  takes  fire  even  in  the  flame  of  a  candle,  and  burns 
with  dazzling  brilliancy.  The  result  is  magnesia, 
so  much  used  as  a  medicine.  Unite  magnesia  to 
silica,  and  we  have,  according  to  the  proportions, 
hornblende  or  augite,  two  minerals  which  abound  in 
many  varieties  of  rock.  Add  water  to  the  composi- 
tion, and  we  get  also  serpentine  or  soapstone,  with 
several  other  allied  mineral  species. 

I  might  multiply  these  illustrations  indefinitely, 
but  I  will  limit  myself  to  only  one  other  example. 
Here  is  a  metallic  element  called  potassium,  so  light 
and  combustible  that  it  swims  and  burns  on  water. 
Burning  in  water  may  seem,  at  first  sight,  very  par- 
adoxical ;  but  in  studying  chemistry  we  must  be 
ready  to  give  up  old  prejudices.  Water  is  almost 
pure  oxygen,  containing  in  the  same  volume  more 
than  one  hundred  times  as  much  of  the  fire-element 
as  air,  and  all  combustibles  would  burn  in  water 
were  it  not  that  the  oxygen  is  imprisoned  in  the 
liquid  by  an  immensely  strong  force.  Potassium, 
however,  has  such  intense  chemical  affinities  that  it 
will  break  through  all  bars  and  bolts  in  order  to  unite 
with  oxygen,  and  it  therefore  burns  thus  brilliantly 
even  in  the  midst  of  water.^     The  final  result  is  a 

*  The  flame  in  this  experiment  is  caused  by  the  burning  of  the 
hydrogen  gas,  which  is  one  of  the  products  of  the  chemical  action. 


92 


WORLD-BUILDING. 


white  solid  called  potash,  which  dissolves  in  the  liq- 
uid. Melt  together,  now,  potash,  lime,  and  silicious 
sand,  and  we  have  glass.  Un'te  silica,  alumina,  and 
potash,  and  we  get  feldspar ;  combine  them  in  differ- 
ent proportions,  and  we  have  mica  ;  varying  again 
the  proportions,  we  obtain  garnet.  Lastly,  mix 
quartz  and  feldspar  together  with  mica  or  horn- 
blende, in  an  indiscriminate  jumble,  and  we  have 
the  several  varieties  of  granitic  rocks. 

Such,  then,  are  some  of  the  steps  in  the  process 
of  world-building.  I  do  not  mean  to  imply  that  we 
can  reproduce  all  these  substances  in  our  laborato- 
ries, although  even  this  is  true  in  almost  every  case. 
My  object  is  only  to  show  what  must  have  been  in 
general  the  process  of  nature,  and  to  make  evident 
the   fact   that   oxygen  has   been   the    chief  world- 


Oxygen, 

Silicon, 

Aluminum. 
Magnesium. 
Calcium. 

K,  Na,  Fe,  C. 

S,  H,  CI,  N.   57  others. 

builder.  But  why  call  oxygen  the  world-builder 
more  than  the  other  elements  ?  This  diagram  an- 
swers the  question,  and  it  illustrates  one  of  the  most 


WORLD-BUILDING.  93 

remarkable  facts  to  which  the  study  of  this  func- 
tion of  oxygen  has  led.  Of  the  seventy  known  ele- 
ments, more  or  less,  thirteen  alone  make  up  at  least 
y%^(j  of  the  whole  known  mass  of  the  earth.  Of  this, 
oxygen  forms  about  ^,  silicon  about  ^  ;  then  we 
have  aluminum,  magnesium,  calcium,  potassium  (K), 
sodium  (Na),  iron  (Fe),  carbon  (C),  sulphur  (S),  hy- 
drogen (H),  chlorine  (CI),  and  nitrogen  (N)  filling  up 
nearly  the  other  fourth,  while  the  remaining  ele- 
ments— including  all  the  useful  metals  except  iron — 
do  not  constitute  altogether  more  than  j^-^.  The  di- 
agram, however,  only  represents  the  relative  propor- 
tions very  rudely,  as  the  subdivisions  are  necessarily 
based  on  very  rough  estimates  and  imperfect  data. 

Evidently,  then,  so  far  as  our  knowledge  extends, 
oxygen,  silicon,  and  carbon,  together  with  a  few 
metals,  have  been  the  chief  building-materials  em- 
ployed by  the  Great  Architect,  and  oxygen  has 
been,  as  it  were,  the  universal  cement  by  which  the 
other  elements  have  been  joined  together  to  form 
that  grand  and  diversified  whole  we  call  our  earth. 

One  more  remark  in  regard  to  this  subject,  and  I 
will  close  this  chapter.  It  is  probable  that  there 
was  a  time,  anterior  to  the  earliest  geological  rec- 
ords, when  the  elements  were  in  a  free  state; 
when  the  oxygen  now  solidified  was  a  gas,  and 
when,  at  the  appointed  time,  the  union  of  the 
elements  began.  Then  our  earth  was  a  bright, 
burning  star,  radiating  heat  and  light  into  space. 
Indeed,  if  we  accept  the  nebular  hypothesis  of 
Laplace,  the  earth  was  formerly  a  part  of  the  sun, 
was  thrown  off  by  the   centrifugal   force    from  his 


94  WORLD-BUILDING. 

burning  mass,  and,  like  a  spark  from  a  forge,  soon 
burnt  out,  although  after  this  lapse  of  time  the  great 
central  fire  is  burning  still.  But  whether  Laplace  be 
right  or  not,  this  much  is  certain  ; — the  crust  of  the 
earth,  so  far  as  we  can  examine  it,  is  like  a  burnt 
cinder,  and  'the  atmosphere  of  oxygen  which  sur- 
rounds it  is  merely  the  residuum  left  after  the  gen- 
eral conflagration, — left  because  there  was  nothing 
more  to  burn.  Unmeasured  ages  have  passed  away 
since  then  ;  the  earth's  crust  has  cooled  and  solidi- 
fied ;  the  waters  have  been  condensed  and  gathered 
into  the  great  ocean-basins ;  the  dry  land  has  been 
covered  with  verdure  and  peopled  with  all  kinds  of 
four-footed  beasts,  winged  fowls,  and  creeping  things  ; 
the  waters  have  been  tenanted  with  countless  forms 
of  swimming  creatures;  and,  last  of  all,  man  has 
come  to  live  in  this  fair  creation,  and  study  the  won- 
ders of  his  dwelling-place.  He  finds  on  the  earth's 
burnt  crust  an  abundant  supply  of  combustible  ma- 
terial for  all  his  wants.  But  if  the  world  was  once 
burnt  up,  and  the  elements  glowed  with  fervent  heat, 
how  is  it  that  these  combustibles  have  been  left  un- 
consumed  ?  Modern  science  has  been  able  to  an- 
swer this  question.  It  has  discovered  that  during 
the  long  geological  periods  a  silent  agency  has  been 
slowly  recovering  a  small  amount  of  combustible 
material  from  the  wreck  of  the  first  conflagration. 
The  sunbeam  has  partly  undone  the  work  of  the 
fire,  and  whatever  now  exists  on  the  earth  unburnt, 
wood,  coal,  or  metal,  we  owe  to  that  wonderful  agent 
the  solar  light.  How  the  result  has  been  accom- 
plished, I  propose  to  consider  in  a  future  chapter. 


f  LIBRARY  "^ 

UNIA^EHSITY   OF 

^  CALIFOKNIA.  , 


CHAPTER   IV.- 
TESTIMONY  OF  OXYGEN — Concluded. 

Besides  the  two  extreme  conditions  of  oxygen,  . 
there  exists  still  a  third,  in  a  measure  intermediate 
between  them,  but  still  differing  essentially  from 
either, — a  condition  in  which  the  element  discharges 
functions,  less  brilliant  it  is  true,  but  not  less  inter- 
esting and  instructive,  than  those  which  we  studied 
in  the  last  chapter.  The  phenomena  in  which  this 
condition  of  oxygen  is  chiefly  active  require,  as  a 
general  rule,  months,  or  even  years,  for  their  full 
manifestation.  Moreover,  they  are  so  silent  and 
unobtrusive,  as  frequently  to  be  passed  unnoticed  ; 
but  nevertheless,  when  we  have  become  acquainted 
with  their  magnitude  and  importance,  I  am  sure  you 
will  agree  with  me  that  they  far  surpass  in  true 
grandeur  those  dazzling  displays  of  power  which  the 
fire-element  manifests  when  fully  aroused.  This 
third  phase  of  the  element  can  be  best  studied  in 
its  effects,  and  to  two  of  these  I  now  ask  your 
attention. 

Every  one  knows  that,  when  wood  or  any  other 
organized  structure  is  exposed  to  the  moist  atmos- 
phere, it  gradually  decays.     It  first  becomes  rotten, 

95 


96  DECAY. 


and  then  slowly  disappears.  All  may  not  know, 
however,  that  decay  consists  in  a  slow  union  of  the 
organized  structure  with  oxygen,  and  that  the  log 
of  wood  which  is  left  to  rot  in  the  forest  undergoes 
precisely  the  same  change  as  one  which  is  burnt  on 
the  hearth.  The  sole  difference  is,  that,  while  the 
last  is  burned  up  in  a  few  hours,  the  first  entirely 
disappears  only  after  the  lapse  of  many  years. 
Wood,  like  all  organized  vegetable  structures,  con- 
sists mainly  of  three  elements,  carbon,  hydrogen, 
and  oxygen.  When  heated  on  the  hearth,  in  con- 
tact with  the  air,  it  takes  fire  and  burns  ;  that  is,  its 
combustible  elements  combine  with  oxygen,  the 
carbon  to  form  carbonic  dioxide,  and  the  hydrogen 
to  form  aqueous  vapor,  both  of  which  escape  by  the 
chimney.  But  of  these  two  ingredients  of  the  wood, 
hydrogen  is  by  far  the  most  combustible ;  that  is,  it 
has  the  greatest  tendency  to  combine  with  oxygen, 
and  therefore  burns  first,  leaving  the  less  combus- 
tible carbon  in  the  form  of  glowing  coals.  If  at 
this  point  we  take  up  one  of  these  coals  and  quench 
it  in  water,  it  will  be  found  to  be  common  black 
charcoal ;  but  if  left  on  the  hearth,  the  coal  also 
burns,  gradually  smouldering  away,  and  passing  up 
the  chimney  as  carbonic  dioxide  gas. 

Quite  a  similar  succession  of  phenomena  is  pre- 
sented in  the  forest  during  the  process  of  decay.  In 
decay,  as  in  burning,  the  oxygen  of  the  air  unites 
with  the  hydrogen  of  the  wood  more  rapidly  than 
with  the  carbon,  and  in  consequence  the  rotten 
wood  becomes  darker  and  darker,  from  the  excess  of 
black  charcoal,  as  the  change  advances.     Moreover, 


DECAY.  97 

if  the  supply  of  air  is  insufficient,  as  when  the  wood 
is  buried  in  swamps,  it  is  finally  reduced  to  coal, 
which  corresponds  to  half-burnt  wood.  In  the  open 
air,  however,  the  charcoal  as  well  as  the  hydrogen  is 
burnt,  and  the  log  of  wood  is  resolved,  as  in  ordinary 
combustion,  into  carbonic  dioxide  and  water,  leaving 
only  a  few  handfuls  of  earth  to  mark  the  spot  where 
it  lay.  This  change  requires  years  before  it  is  fully 
consummated,  and  it  is  not  therefore  wonderful  that 
its  nature  should  not  have  been  understood  until  a 
comparatively  recent  period.  Thanks  to  modern 
chemistry,  the  subject  is  now  less  obscure.  We  may 
not  be  able  to  trace  all  the  steps  of  the  process,  but 
this  much  we  know.  Decay  and  burning  are  essen- 
tially the  same  chemical  change.  The  substances 
involved  are  the  same,  the  results  are  the  same,  and 
we  have  even  been  able  to  prove  that  the  amount 
of  heat  generated  is  the  same,  the  only  difference 
being,  that,  in  burning,  the  whole  amount  of  heat  is 
set  free  in  a  few  hours,  producing  phenomena  of  in- 
tense ignition  ;  while  in  the  process  of  decay  the 
same  quantity,  slowly  evolved  during  perhaps  a 
century,  escapes  notice. 

It  has  been  observed,  that,  if  wood  be  left  in 
contact  with  dry  oxygen,  it  may  be  kept  indefinitely 
without  undergoing  change, — a  fact  sufficiently 
proved  by  the  mummy  cases  of  Egypt,  which  in 
that  dry  climate  have  been  preserved  for  over  three 
thousand  years  ; — also,  that  if  wood  is  impregnated 
with  certain  salts,  as  in  the  process  of  Kyanizing  or 
Burnetizing,  decay  may  be  arrested,  even  in  a  damp 
situation,  for  a  long  time.  In  both  cases  the  pre- 
5 


98  DECAY. 

vention  depends  on  destroying  certain  very  unstable 
compounds  which  are  present  in  all  green  wood,  and 
which  start  the  decay.  These  are  termed  by  chemists 
albuminous  substances,  the  chief  of  which,  vegetable 
albumen^  is  almost  identical  with  the  white  of  an 
egg.  The  great  bulk  of  all  vegetable  structures,  as 
was  stated  above,  consists  of  only  three  elements, 
carbon,  hydrogen,  and  oxygen ;  but  these  albumi- 
nous substances — which,  as  a  rule,  are  present  only 
in  very  small  quantities — contain,  in  addition  to  the 
three  just  mentioned,  a  fourth  element,  nitrogen. 
Partly  because  they  contain  nitrogen,  and  partly, 
unquestionably,  in  consequence  of  the  complex  man- 
ner in  which  the  four  elements  are  combined,  the 
albuminous  substances  are  vastly  more  unstable  than 
the  great  mass  of  vegetable  matter,  and  in  the 
presence  of  moisture  they  soon  undergo  an  internal 
change,  called  putrefaction,  or  fermentation,  by 
which  they  are  broken  up  into  simpler  compounds. 
The  precise  nature  of  the  process  is  not  understood, 
but  nothing  appears  to  be  added  to  the  substance, 
unless  it  be  water,  and  the  change  seems  to  consist 
in  the  falling  to  pieces  of  a  complex  organic  structure. 
At  all  events,  oxygen  gas  is  not  essential  to  the  pro- 
cess, but  the  oxygen  of  the  air  which  happens  to  be 
in  contact  with  the  fermenting  substances,  in  some 
mysterious  way,  undergoes  a  remarkable  change. 
It  becomes  endowed  with  active  properties  even  at 
the  ordinary  temperature,  and_,  with  its  affinities  thus 
exalted,  slowly  consumes  the  wood,  together  with 
all  other  organic  compounds  present.  Moreover,  the 
process,  once  started,  sustains  itself.     As,  in  burning, 


DECAY.  99 

the  union  of  the  combustible  matter  with  oxygen 
engenders  sufficient  heat  to  maintain  the  surround- 
ing gas  in  its  highly  active  modification,  so  in  like 
manner  the  process  of  decay  seems  to  modify  con- 
tinually the  neighboring  oxygen,  arousing  its  ener- 
gies, and  thus  continuing  the  change. when  once 
begun. 

While  the  plant  is  in  great  measure  made  up  of 
non-nitrogenized  substances,  the  anirhal,  on  the 
other  hand,  consists  almost  entirely  of  albuminous 
compounds.  The  flesh,  the  nerves,  and  the  bones 
of  our  bodies  all  contain  nitrogen,  and,  like  the  vege- 
table albumen,  are  prone  to  decay ;  and  this  change 
is  constantly  going  on  in  our  living  members.  In  a 
most  profound  sense,  "  in  the  midst  of  life  we  are  in 
death.'*  The  materials  of  our  bodies  are  being  con- 
stantly renewed,  and  the  great  mass  of  their  struc- 
ture changes  in  less  than  a  year."^  At  every  motion 
of  your  arm,  and  at  every  breath  you  draw,  a  portion 
of  the  muscles  concerned  is  actually  burnt  up  in  the 
effort.  During  life,  in  some  utterly  mysterious  man- 
ner, beyond  the  range  of  all  human  science,  the 
various  gases  and  vapors  of  the  atmosphere,  to- 
gether with  a  small  amount  of  a  few  earthy  salts, 
are  elaborated  into  various  organized  structures. 
They  first  pass  into  the  organism  of  the  plant,  and 

*  The  rapidity  of  the  change  has  not  been  accurately  determined. 
Some  authors  state  that  the  great  mass  of  the  body  changes  every 
month,  and  when  we  consider  the  large  quantities  of  water,  carbonic 
dioxide,  and  ammonia  daily  secreted,  the  statement^appears  credible  ; 
but  in  the  absence  of  direct  proof  we  have  set  the  limit  unnecessarily 
high  in  order  to  avoid  the  slightest  exaggeration. 


ICX)  DOCTRINE  OF  THE   RESURRECTION. 

thence  are  transferred  to  the  body  of  the  animal ; 
but  no  sooner  are  they  firmly  built  into  the  animal 
tissues,  than  a  destructive  change  begins,  by  which 
before  long  they  are  restored  to  the  air  or  the  soil, 
only  to  renew  the  same  cycle  of  ceaseless  change. 
Life,  during  its  whole  existence,  is  an  untiring 
builder,  the  oxygen  of  the  atmosphere  a  fell  de- 
stroyer; and  when  at  last  the  builders  cease,  then 
the  spirit  takes  it  heavenward  flight,  and  leaves  the 
frail  tenement  to  its  appointed  end.  Dust  returns 
to  the  dust,  and  these  mortal  mists  and  vapors  to 
the  air. 

I  know  that  there  are  some  who  entertain  a  vague 
fear  that  these  well-established  facts  of  chemistry 
conflict  with  one  of  the  most  cherished  doctrines  of 
the  Christian  faith  ;  but  so  far  from  this,  I  find  that 
they  elucidate  and  confirm  it.  I  admit  that  they  do 
disprove  that  interpretation  frequently  given  to  the 
doctrine  of  the  resurrection,  which  assumes  that 
these  same  material  atoms  will  form  parts  of  our 
celestial  bodies ;  but  then  I  find  that  this  interpre- 
tation is  as  much  opposed  to  Scripture  as  to  science. 
The  Saviour  himself,  in  his  reply  to  the  incredulous 
Sadducees,  severely  rebuked  such  a  material  con- 
ception of  his  spiritual  revelation,  and  the  great 
Apostle  to  the  Gentiles,  in  his  vision  of  the  glorified 
body,  distinctly  declares  that  this  body  is  not  the 
body  that  shall  be  ;  but  that,  as  the  grain  sown  in 
the  furrow  rises  into  the  glory  of  the  full-eared  corn, 
"  so  when  this  corruptible  shall  have  put  on  incor- 
ruption,  and  this  mortal  shall  have  put  on  immortal- 
ity,*' our  natural  body,  sown  in  dishonor  and  weak- 


DOCTRINE   OF  THE   RESURRECTION.  lOI 

ness,  will  be  raised  a  spiritual  body,  clothed  in  glory 
and  in  power.  "  And  as  we  have  borne  the  image 
of  the  earthy,  we  shall  also  bear  the  image  of  the 
heavenly/* 

The  glorious  doctrine  of  the  resurrection  here  pre- 
sented, modern  scientific  discoveries  most  fully  con- 
firm. They  have  shown  that  our  only  abiding  sub- 
stance is  merely  the  passing  shadow  of  our  outward 
form,  that  these  bones  and  muscles  are  dying  within 
us  every  day,  that  our  whole  life  is  an  unceasing 
metempsychosis,  and  that  the  final  death  is  but  one 
phase  of  the  perpetual  change.  Thus  the  idea  of  a 
spiritual  body  becomes  not  only  a  possible  concep- 
tion, but,  more  than  this,  it  harmonizes  with  the 
whole  order  of  nature ;  and  now  that  we  can  better 
trace  the  processes  of  growth  in  the  organic  world, 
and  understand  more  of  their  hidden  secrets,  the  in- 
spired words  of  Paul  have  acquired  fresh  power,  and 
convey  to  us  a  deeper  meaning  than  they  ever  gave 
to  the  early  Fathers  of  the  Church.  It  is  no  wonder 
that,  when  men  were  less  enlightened,  the  doctrine 
should  have  been  misinterpreted  ;  but  now,  when 
the  truth  has  been  illuminated  by  the  study  of  na- 
ture, why  longer  harass  the  understanding  and  vex 
the  spirit  with  these  material  clogs?  Hear  again 
the  words  of  the  Apostle :  "  This  I  say,  brethren, 
that  flesh  and  blood  cannot  inherit  the  kingdom 
of  God  ;  neither  doth  corruption  inherit  in  corrup- 
tion." "  For  this  corruptible  must  put  on  incorrup- 
tion,  and  this  mortal  must  put  on  immortality.'*  And 
now,  turning  to  the  glorious  truth  as  Christ  revealed 
it  and   Paul  preached   it,  how  greatly  is  our  faith 


I02  DOCTRINE  OF  THE   RESURRECTION. 

strengthened  by  these  lights  of  nature  !  All  philos- 
ophy assures  us  that  the  finite  and  limited  can  be 
manifested  only  under  form. 

'^That  each,  who  seems  a  separate  whole, 
Should  move  his  rounds,  and,  fusing  all 
The  skirts  of  self  again,  should  fall 
Remerging  in  the  general  Soul, 

*'  Is  faith  as  vague  as  all  un sweet : 
Eternal  form  shall  still  divide 
The  eternal  soul  from  all  beside  ; 
And  I  shall  know  him  when  we  meet.'' 

Chemistry  has  shown  us  that  it  is  the  form  alone  of 
our  mortal  bodies  which  is  permanent,  and  that  we 
retain  our  personality  under  constant  change;  and 
I  lastly,  in  organic  nature,  the  sprouting  of  the  seed, 
the  breaking  of  the  bird  from  the  egg,  the  bursting 
of  the  butterfly  from  the  chrysalis,  and  ten  thousand 
other  transmutations  not  less  wonderful,  which  we 
are  daily  witnessing  around  us,  all  unite  their  analogies 
to  elucidate  and  confirm  the  glorious  and  comforting 
doctrine  of  a  material  resurrection  in  form. 

Moreover,  when  we  remember  that  our  organs  of 
vision  and  hearing  are  capable  of  receiving  impres- 
sions either  of  light  or  sound  only  when  the  rapidity 
of  the  undulations  which  cause  them  is  comprised 
within  certain  very  narrow  limits,  and  when  we  re- 
call the  facts  stated  in  a  previous  chapter,  that  there 
are  waves  of  light  and  sound  of  which  our  dull 
senses  take  no  cognizance,  that  there  is  a  great  dif- 
ference even  in  human  perceptivity,  and  that  some 


GHOSTLY  OFFICE  OF  OXYGEN.  I03 

men,  more  gifted  than  others,  can  see  colors  or 
hear  sounds  which  are  invisible  or  inaudible  to  the 
great  bulk  of  mankind,  you  will  appreciate  how 
possible  it  is  that  there  may  be  a  world  of  spiritual 
existence  around  us — inhabiting  this  same  globe, 
enjoying  this  same  nature — of  which  we  have  no 
perception ;  that,  in  fact,  the  wonders  of  the  New 
Jerusalem  may  be  in  our  midst,  and  the  song  of  the 
angelic  hosts  filling  the  air  with  celestial  harmony, 
although  unheard  and  unseen  by  us.  Let  me 
not  be  understood  as  implying  that  science  has  in. 
any  sense  revealed  to  us  a  spiritual  world,  or  that 
it  gives  the  slightest  shadow  of  support  to  those 
products  of  imposture,  credulity,  and  superstition, 
which,  under  the  name  of  witchcraft,  mesmerism,  or 
spiritualism,  have  in  every  age  of  the  world  de- 
ceived so  many.  The  only  revelation  man  has  re- 
ceived of  a  spiritual  existence  is  recorded  in  the 
Bible;  but  modern  science  has  rendered  the  concep- 
tion of  such  an  existence  possible,  and  in  this  way  has 
removed  a  source  of  doubt.  The  materialist  can  no 
longer  say  that  the  spiritual  world  is  inconceivable ; 
for  these  discoveries  show  that  it  may  be  included 
in  the  very  scheme  of  nature  in  which  we  live,  and 
thus,  although  science  may  not  remove  the  veil,  it 
at  least  answers  this  cavil  of  materialism. 

Returning  now  to  the  main  subject,  consider  for 
a  moment  the  importance  of  this  ghostly  office  of 
oxygen  in  the  scheme  of  organic  nature.  Reflect 
how  soon  this  fair  world  would  become  a  great 
charnel-house  were  it  not  for  these  provisions,  by 
which  its  youth  is  constantly  renewed.     Remember 


IC4  RESPIRATION. 


also  that  this  process  of  decay  furnishes  the  mate- 
rials from  which  young  life  builds  her  fresh  and 
blooming  forms ;  that,  although  in  the  midst  of  life 
we  are  in  death,  it  is  equally  true  that  death  is  only 
a  phase  of  life.  Then  these  changes  of  outward 
nature  will  assume  a  new  aspect.  It  will  be  seen 
that  they  are  the  beneficent  provisions  of  infinite 
wisdom,  in  themselves  full  of  interest  and  beauty, 
and  only  sad  and  melancholy  as  they  are  associated 
with  bereaved  affections  and  disappointed  hopes,  or 
with  that  only  real  death,  the  moral  death  of  the 
soul.  **  O  death,  where  is  thy  sting  ?  O  grave, 
where  is  thy  victory?  The  sting  of  death  is  sin; 
and  the  strength  of  sin  is  the  law.  But  thanks  be 
to  God,  which  giveth  us  the  victory  through  our 
Lord  Jesus  Christ." 

I  might  profitably  occupy  several  hours  in  de- 
scribing the  various  processes  of  slow  combustion, 
for  they  are  all  rich  in  illustrations  of  skilful  design ; 
but  I  must  content  myself  with  only  one  other  ex- 
ample, and  from  the  many  which  crowd  upon  me  I 
have  chosen  respiration,  because  it  is  so  well  under- 
stood and  because  it  is  so  intimately  associated  with 
our  own  physical  existence.  Respiration  is  a  true 
example  of  combustion.  The  seat  of  the  combustion 
is  the  lungs.  The  substance  burnt  is  sugar.  The 
products  are  carbonic  dioxide  gas  and  water. 

The  materials  of  animal  food  may  be  divided  into 
three  classes :  non-nitrogenized  substances,  such  as 
starch  and  sugar ;  nitrogenized  substances,  like  lean 
meat  and  eggs  ;  and,  lastly,  fatty  substances,  like 
butter.     To  these  must  be  added  a  small  proportion 


RESPIRATION.  I05 


of  earthy  salts,  which,  however,  as  they  enter  into 
the  composition  of  almost  all  varieties  of  food,  do 
not  properly  form  a  distinct  class.  All  of  the  three 
classes  of  food  are  absolutely  necessary  to  support 
the  life  of  the  higher  animals,  and  especially  of  man, 
and  they  are  all  contained  in  those  articles  of  diet 
which  will  of  themselves  alone  sustain  life.  Milk 
may  be  regarded  as  the  type  of  animal  food. 

Composition  of  Milk* 

Natural  State.  ^^^^^^^ 

Water 87 

Curd  or  casein a^\  34f 

Butter  or  fat 3  23^ 

Sugar  (of  milk) 4f  37 

Ash  (nearly) f  At\      '"^ 

100  100 

It  contains,  in  the  first  place,  a  non-nitrogenized 
substance,  sugar;  in  the  second  place,  a  nitrogen- 
ized  substance,  casein,  which  separated  from  milk 
forms  cheese ;  and,  lastly,  a  fatty  substance,  which 
when  separated  by  churning  forms  butter. 

Wheaten  Bread.      Lean  Beef. 

Water 45  78 

Fibrin  or  gluten 6  19 

Fat I  3 

Starch,  etc 48 

100  100 

Bread,  again  ;  consists  of  starch,  a  non-nitrogne- 
ized  substance ;  of  gluten,  a  nitrogenized  substance, 

*  Johnston's  Chemistry  of  Common  Life. 


I06  RESPIRATION. 


and  it  also  contains  about  two  per  cent,  of  a  peculiar 
oil.  No  article  of  food  which  does  not  contain  all 
three  of  these  classes  of  substances  can  alone  sup- 
port life  for  any  length  of  time.  A  man  would 
starve  to  death  on  starch  alone,  on  meat  alone,  or 
on  butter  alone.  The  relative  proportion,  however, 
in  which  these  three  classes  of  substances  are  re- 
quired by  man,  depends  on  his  outward  circum- 
stances, such  as  the  climate,  his  physical  activity,  his 
occupation,  or  his  peculiar  temperament,  and  to  the 
right  balance  of  his  food  he  is  guided  by  experience. 

The  different  classes  of  food  serve  different  func- 
tions in  the  body.  The  nitrogenized  and  a  portion 
of  the  fatty  substances  are  used  to  supply  the  con- 
stant waste  of  the  tissues  which  results  from  all  the 
animal  processes.  They  are  in  some  unknown  way 
vitalized  in  the  system,  and  converted  into  new 
muscles,  tendons,  and  nerves,  which  take  the  place 
of  those  that  have  been  used  up.  On  the  other 
hand,  the  non-nitrogenized  substances,  such  as 
starch,  are  supposed  to  take  no  part  in  the  for- 
mation of  new  tissues,  and  to  be  merely  the  fuel 
by  which  the  animal  heat  is  maintained.  Let  us 
very  briefly  follow  these  substances  through  the 
body,  and  see  when  and  how  they  are  burnt. 

By  far  the  greater  part  of  our  daily  food  consists 
of  varieties  of  starch  or  sugar.  These  two  sub- 
stances are  almost  identical  in  composition,  and 
starch  may  be  converted  into  sugar  with  the  great- 
est ease.  Leaving  out  of  view  the  large  amount  of 
water  which  all  our  food  contains,  we  find  that  of 
wheaten  bread  no  less  than    39   per  cent,  consists 


RESPIRATION.  10/ 


of  starch  or  sugar ;  of  potatoes  fully  92  per  cent, 
is  made  up  of  the  same  materials,  and  in  general 
they  form  over  four-fifths  of  the  solid  part  of  all 
our  food.  These  substances  when  taken  into  the 
stomach  are  almost  instantaneously  converted  by 
the  saliva  and  the  gastric  juice  into  the  variety 
of  sugar  known  as  grape-sugar,  so  called  because 
it  is  the  sweet  principle  of  ripe  grapes.  The  sweet 
principle  of  honey  and  molasses,  and  the  incrusta- 
tion which  is  so  frequently  seen  on  figs  and  raisins, 
are  also  essentially  the  same  substance.  Grape- 
sugar,  being  very  soluble,  dissolves  in  the  water 
present,  and  the  solution  is  absorbed  by  the  veins 
which  ramify  on  the  surface  of  the  intestinal  canal, 
into  which  the  digested  food  passes  from  the 
stomach.  The  blood,  now  containing  sugar  in  so- 
lution, returns  through  the  liver  to  the  right  side 
of  the  heart,  and  by  this  organ,  which  consists  es- 
sentially of  two  ingeniously  contrived  force-pumps, 
arranged  side  by  side,  it  is  forced  through  the  lungs, 
where  the  sugar  is  brought  in  contact  with  the  air. 
Let  us  next  examine  for  a  moment  this  remarkable 
structure. 

The  lungs,  as  is  well  known,  consist  of  two  large 
organs,  on  either  side  of  the  chest,  called  the  left 
and  the  right  lung.  The  right  lung  is  divided  into 
three  smaller  lungs,  called  lobes,  the  left  into  but 
two..  On  examining  any  one  of  these  lobes  it  will 
be  found  to  be  made  up  of  an  immense  number 
of  small  membranous  bags,  all  closely  packed  to- 
gether. These  small  bags,  called  cells,  connect 
by  means  of  the  bronchial  tubes  and  windpipe  with 


I08  RESPIRATION. 


the  air,  through  the  nose  and  mouth.  They  vary 
in  size,  but  on  an  average  are  about  y^  of  an 
inch  in  diameter,  and  the  total  number  of  the 
cells  in  the  lungs  has  been  estimated  at  six  hun- 
dred millions.  Their  walls  are  exceedingly  -thin, 
and  the  cells  may  therefore  be  easily  compressed. 
The  whole  mass  of  the  lungs  is  also  exceedingly 
elastic,  and  by  the  action  of  a  system  of  muscles 
their  volume  is  alternately  increased  and  dimin- 
ished in  the  process  of  respiration.  The  amount 
of  air  which  is  thus  drawn  into  the  cells,  and  again 
expelled  at  each  inspiration,  differs  in  different  indi- 
viduals. The  average  quantity  in  the  ordinary  tran- 
quil respiration  of  an  adult  is  about  a  pint ;  but  in  a 
full  respiration  it  may  be  as  much  as  two  and  a  half 
pints,  and  by  an  effort  the  lungs  may  be  made  to 
inhale  from  five  to  seven  pints.  As  the  average  in 
health  is  about  eighteen  inspirations  a  minute,  which 
corresponds  to  about  eighteen  pints  of  air  inhaled 
and  exhaled,  it  follows  that  three  thousand  gal- 
lons of  air  pass  through  the  lungs  of  an  adult  man 
every  day.  Some  estimate  it  as  high  as  four  thou- 
sand gallons  a  day  for  an  average  man  in  average 
circumstances,  and  as  high  as  five  thousand  seven 
hundred  gallons  a  day  for  an  athletic  man  under- 
going severe  exertion.  In  order  that  you  may  form 
an  idea  of  this  quantity,  I  will  add  that  four  thou- 
sand gallons  of  air  would  fill  a  room  measuring  about 
eight  and  a  half  feet  in  each  dimension. 

Let  us  now  turn  to  the  blood,  and  examine  the 
apparatus  by  which  it  is  exposed  to  the  air  in 
the   lungs.      As  we   have    already  seen,    the  blood 


RESPIRATION.  lOg 


charged  with  sugar  is  received  into  the  heart,  from 
whence  it  is  pumped  through  a  long  tube,  called 
the  pulmonary  artery,  into  the  lungs.  This  artery 
divides  again  and  again  until  it  is  reduced  to  very 
small  capillary  tubes,  which  ramify  on  the  surfaces 
of  the  air-cells.  The  walls  of  these  capillaries  are 
formed  of  the  thinnest  conceivable  membrane,  so 
as  to  bring  the  blood  into  as  close  contact  as  pos- 
sible with  the  air.  Here  oxygen  gas  is  absorbed  in 
large  quantities,  and  carbonic  dioxide  gas  evolved. 
The  blood  now  holds  in  solution  at  the  same  time 
oxygen  gas  and  suga?,  and,  thus  charged,  it  returns, 
by  a  series  of  veins  to  the  left  side  of  the  heart, 
when  by  the  second  of  the  two  force-pumps  it  is 
again  forced  through  the  general  circulation  of  the 
body.  In  the  meantime  the  oxygen  absorbed  by 
the  blood  while  in  the  lungs  burns  up  the  sugar. 
Sugar,  like  wood,  consists  of  carbon,  hydrogen,  and 
oxygen.'  The  last  two  are  present  in  the  pro- 
portions to  form  water,  so  that  sugar  may  be 
said  to  be  composed  of  charcoal  and  water.  Of 
these  two  substances  the  charcoal  only  is  combus- 
tible. This,  during  the  circulation  of  the  blood,  is 
slowly  burnt  up  by  the  dissolved  oxygen,  and 
converted  into  carbonic  dioxide,  which  remains  in 
solution  until  it  is  discharged,  when  the  blood  re- 
turns again  to  the  lungs,  or  else  escapes  through  the 
skin. 

Thus  it  appears  that  respiration  is  a  process  of 
combustion,  in  which  the  fuel  is  sugar,  and  the 
smoke  carbonic  dioxide  and  aqueous  vapor.  I  need 
not   dwell  on   a  fact  so  universally  known   as  the 


no  RESPIRATION. 


presence  of  carbonic  dioxide  in  the  breath.  All, 
however,  may  not  know  how  large  is  the  volume 
of  this  gas  which  they  daily  exhale.  It  varies  with 
age,  sex,  food,  health,  and  a  variety  of  other  cir- 
cumstances. In  a  full-grown  man  the  weight  of 
carbonic  dioxide  evolved  from  the  lungs  varies  from 
one  to  three  pounds  in  twenty-four  hours,  which 
is  equivalent  to  from  nine  to  twenty-seven  cubic 
feet.  During  the  present  lecture  the  amount  of 
carbonic  dioxide  which  has  been  exhaled  into  this 
room  by  the  audience  is  equal  to  at  least  seven 
hundred  and  fifty  cubic  feef,^  and  would  fill  a 
room  measuring  about  nine  feet  in  each  direction. 
From  the  quantity  of  carbonic  dioxide  gas  exhaled 
we  can  very  readily  calculate  the  amount  of  char- 
coal burnt,  which  in  a  full-grown  man  will  vary 
from  five  to  fifteen  ounces  in  twenty-four  hours. 
Hence,  the  amount  of  charcoal  which,  in  the  form 
of  sugar,  has  been  burnt  up^  in  the  lungs  of  the 
audience  during  the  last  hour,  is  equal  to  at  least 
fifteen  pounds,^  which  I  have  had  weighed  out 
and  placed  on  the  lecture  table,  in  order  to  give 
you  an  idea  of  the  quantity.  Moreover,  it  has 
been  proved  that  the  quantity  of  heat  evolved  by 
a  given  amount  of  charcoal  in  burning  is  abso- 
lutely the  same,  whether  the  combustion  be  rapid 
or  slow,  so  that  the  same  amount  of  heat  has  been 
generated  in  our  bodies  during  the  last  hour  by 
the  slow  process  of  respiration  as  would  have  been 
set  free  by  burning  this  basketful  of  charcoal.     It 

*  Calculated  for  one  thousand  persons. 


RESPIRATION.  1 1 1 


is  no  wonder,  then,  that  the  temperature  of  the 
body  is  always  so  much  above  that  of  the  air,  and 
that  even  in  the  coldest  climate  the  heat  of  the 
blood  is  maintained  as  high  as  ninety-six  degrees. 
In  regulating  the  temperature  of  his  body,  man 
follows  instinctively  the  same  rules  of  common- 
sense  which  he  applies  in  warming  his  dwellings. 
In  proportion  as  the  climate  is  cold,  he  supplies  the 
loss  of  heat  by  burning  more  fuel  in  his  lungs,  and 
hence  the  statements  of  arctic  voyagers,  who  have 
told  us  that  twelve  pounds  of  tallow-candles  make 
only  an  average  meal  for  an  Esquimaux,  are  not 
inconsistent  with  the  deductions  of  science. 

Respiration,  then,  like  decay,  is  a  process  of  slow 
cojnbustion,  in  which  the  oxygen  of  the  air  attacks 
and  consumes,  even  at  the  ordinary  temperature,  the 
sugar  in  the  blood.  Let  us  now  compare  with  it 
the  rapid  combustion  of  the  same  substance.  Dur- 
ing this  lecture  every  robust  man  present  has,  on  an 
average,  burnt  up  the  equivalent  of  about  one  ounce 
of  sugar.  This  combustion  has  taken  place  so  quiet- 
ly, and  has  set  free  the  requisite  amount  of  heat  so 
gradually,  that  we  have  not  been  conscious  of  it.  In 
the  blood,  where  the  burning  has  been  going  on,  sugar 
and  oxygen,  as  we  have  seen,  are  in  close  contact. 
In  this  crucible  I  have  mixed  together  just  one  ounce 
of  sugar  and  one  and  one-eighth  ounces  of  solidified 
oxygen,  solidified  by  the  force  of  chemical  affinity 
and  bound  up  in  a  white  salt  called  chlorate  of  pot- 
ash. The  oxygen  and  sugar  are  therefore  here  lying 
side  by  side,  as  in  the  blood,  but  the  conditions  of 
slow  combustion  which  exist  in  the  body  not  being 


112  -JIESPIRATION. 


present  in  the  crucible,  they  will  remain  in  contact 
indefinitely,  until  some  external  agency  is  applied. 
The  oxygen  is  now  in  its  passive  condition,  but  a 
single  drop  of  sulphuric  acid  will  arouse  its  dormant 
energies,  and  you  have  instantly  one  of  the  most 
dazzling  displays  of  combustive  energy  which  can  be 
produced  by  art.  The  only  difference  between  this 
brilliant  deflagration  and  the  combustion  which, 
during  the  last  hour,  has  taken  place  in  each  of  our 
bodies,  is  simply  this  :  the  heat  which  in  the  blood 
has  been  imperceptibly  evolved  during  an  hour,  was 
here  concentrated  into  a  few  moments,  and  there- 
fore produced  phenomena  of  intense  ignition.  All 
the  other  conditions, — the  material  burnt,  the  quan- 
tity of  material  employed,  the  products  generated, 
and  the  amount  of  heat  evolved, — are  in  both  cases 
essentially  the  same. 

On  comparing  these  two  phenomena  together,  re- 
flect for  a  moment  on  the  false  estimate  which  we 
are  apt  to  make  of  the  phenomena  of  nature.  The 
splendid  displays  of  combustion  arrest  our  attention 
by  their  very  brilliancy,  while  we  overlook  the  silent 
yet  ceaseless  processes  of  respiration  and  decay,  be- 
fore which,  in  importance  and  magnitude,  the  grand- 
est conflagrations  sink  into  insignificance.  These 
fire  but  the  spasmodic  efforts  of  nature ;  those,  the 
appointed  means  by  which  the  harmony  and  order 
of  creation  are  preserved.  Those  of  us  who  have 
merely  studied  the  brilliant  phenomena  of  nature 
appreciate  but  imperfectly  the  grandeur  of  its  forces, 
and  "  those  of  us  who  limit  our  appreciation  of  the 
powers  of  oxygen  to  the  energies  displayed  by  this 


RESPIRATION.  II 3 


element  in  its  fully  active  state,  form  but  a  very  in- 
adequate idea  of  the  aggregate  results  accomplished 
by  it  in  the  economy  of  the  world. ""^  Contemplate 
the  amount  of  oxygen  employed  in  the  function  of 
respiration  alone.  Faraday  has  roughly  estimated 
that  the  amount  of  oxygen  required  daily  to  supply 
the  lungs  of  the  human  race  is  at  least  one  thousand 
millions  of  pounds  ;  tbat  required  for  the  respiration 
of  the  lower  animals  is  at  least  twice  as  much  as  this, 
while  the  always  active  processes  of  decay  require 
certainly  no  less  than  four  thousand  millions  of 
pounds  more,  making  a  total  aggregate  of  seven 
thousand  millions  of  pounds  required  to  carry  on 
these  processes  of  nature  alone.  Compared  with 
this,  the  one  thousand  millions  of  pounds  which,  as 
Faraday  estimates,  are  sufficient  to  sustain  all  the 
artificial  fires  lighted  by  man,  from  the  camp-fire  of 
the  savage  to  the  roaring  blaze  of  the  blast-furnace 
or  the  raging  flames  of  a  grand  conflagration,  seem 
small  indeed. 


Amount  of  Oxygen  required  Daily. 


* 


Whole  population 1,000,000,000 

Animals 2,000,000,000 

Combustion  and  fermentation. .  . .  1,000,000,000 

Decay  and  other  processes 4,000,000,000 

Oxygen  required  daily =  8,000,000,000  lbs. 


*  Taken  from  Faraday's  Lectures  on  the  Non-Metallic  Elements, 
but  correcting  an  obvious  error  in  reducing  the  pounds  to  tons. 


1 14  RESPIRATION. 


Tons, 
3,571,428  in  a  day.  1 

1,304,642,357  in  a  year. 
Whole  quantity,  1,178,158,000,000,000. 

How  utterly  inconceivable  are  these  numbers, 
which  measure  the  magnitude  of  nature's  processes, 
— eight  thousand  millions  of  pounds  of  oxygen  con- 
sumed in  a  single  day !  When  reduced  to  tons, 
the  numbers  are  equally  beyond  our  grasp,  for  it 
corresponds  to  no  less  than  3,571,428  tons.  If  such 
be  the  daily  requisition  of  this  gas,  will  not  the  oxy- 
gen of  the  atmosphere  be  in  time  exhausted  ?  It  is 
not  difficult  to  calculate  approximately  the  whole 
amount  of  oxygen  in  the  atmosphere.  It  is  equal 
to  about  1,178,158  thousand  millions  of  tons;  a  sup- 
ply which,  at  the  present  rate  of  consumption,  would 
last  about  nine  hundred  thousand  years.  We  need 
not,  therefore,  fear  that  the  amount  of  oxygen  in  the 
atmosphere  will  be  sensibly  diminished  in  our  day  or 
generation  ;  but  then  this  period,  immense  as  it  is, 
is  not  to  be  compared  with  the  ages  of  geological 
time.  The  time  which  has  elapsed  since  the  coal 
we  are  now  burning  was  deposited  in  its  beds  is  to 
be  counted  by  many  millions  of  years,  so  that  since 
the  coal  epoch  the  oxygen  of  the  atmosphere  must 
have  been  all  consumed  again  and  again.  Why, 
then,  has  it  not  all  been  removed  from  the  atmos- 
phere? Simply  because,  in  the  beautiful  balance 
of  creation,  there  is  always  some  recuperative  pro- 
cess for  every  such  loss.  In  the  case  before  us,  it  is, 
as  we  have  seen,    the  vegetation.     As  fast  as  our 


OZONE.  115 


breath,  our  fires,  and  the  process  of  decay  around  us 
are  removing  the  Hfe-giving  oxygen,  just  so  fast  it  is 
restored  by  every  green  leaf  which  waves  in  the  sun- 
shine, and  by  every  blade  of  grass  which  sprouts 
under  our  feet.  What  the  animal  removes,  the  plant 
restores. 

I  have  before  stated  that,  in  the  process  of  decay, 
the  oxygen  of  the  atmosphere,  which  is  active  in 
producing  the  change,  is  undoubtedly  in  a  peculiarly 
modified  condition,  a  condition  in  which  its  affinities 
are  highly  exalted  even  at  the  ordinary  temperature 
of  the  air;  and  I  also  stated  that  this  active  con- 
dition of  the  element  is  apparently  maintained  by 
the  process  of  decay  itself.  This  subject  has  been 
greatly  elucidated  by  modern  discoveries.  Of  all  the 
known  processes  of  slow  combustion,  the  simplest 
and  the  most  active  is  the  slow  combustion  of  phos- 
phorus. This  familiar  substance,  used  to  tip  the 
ends  of  lucifer  matches,  if  exposed  to  the  moist  air, 
slowly  combines  with  oxygen,  shining  at  the  same 
time  in  the  dark  with  a  peculiar  phosphorescent 
light,  whence  the  name  of  the  substance,  from  two 
Greek  words,  signifying  light-bearer.  The  process 
is  therefore  entirely  analogous  to  decay  and  respira- 
tion;  but  since  phosphorus  is  a  chemical  element, 
the  change  is  far  simpler,  and  can  be  more  readily 
studied,  and  for  this  reason  it  may  serve  to  elucidate 
those  more  complex  processes  of  nature. 

Some  years  since.  Professor  Schonbein,  a  distin- 
guished Swiss  chemist,  discovered  that,  while  a  stick 
of  phosphorus  was  slowly  burning  in  a  jar  of  moist 
•air,  a  portion  of  the  oxygen  present  underwent  a 


Il6  OZONE. 


most  remarkable  change.  Without  entering  into 
the  details  of  these  experiments,  I  will  simply  state 
that,  when  thus  modified,  ordinary  oxygen  seems 
entirely  transformed.  The  great  mass  of  the  oxy- 
gen of  the  air,  as  you  will  remember,  is  wholly 
devoid  of  odor,  and  without  action  on  the  most  de- 
licate organic  structures  or  the  most  fleeting  vege- 
table colors;  but  when  thus  treated  it  acquires  a 
very  strong  and  pungent  odor,  rapidly  rusts  polished 
metals,  excites  decay  in  organized  tissues,  and  at 
once  bleaches  the  most  permanent  dyes.  Could 
there  be  a  more  complete  inversion  of  properties  ? 
One  of  the  most  striking  characteristics  of  this  new 
modification  of  oxygen  is  its  peculiar  odor,  and 
hence  Schonbein  calls  it  ozone,  from  a  Greek  verb 
signifying  io  smell.  It  frequently  happens  that  a 
great  discovery  supplies  the  wanting  links  between 
a  number  of  obscure  facts,  and  thus  adds  quite  as 
much  to  our  knowledge  by  its  indirect  bearings  as 
by  the  positive  additions  it  makes  to  the  general 
stock.  So  it  has  been  with  the  discovery  of  ozone. 
Every  one  who  has  used  an  electrical  machine  must 
have  noticed  the  peculiar  smell  which  follows  the 
electrical  discharge.  This  was  formerly  supposed  to 
be  the  odor  of  the  electrical  fluid  itself;  but  as  soon 
as  ozone  was  discovered,  the  odor  was  recognized  at 
once  as  belonging  to  this  new  agent,  and  it  was  soon 
ascertained  that  electricity  is  one  of  the  most  efli- 
cient  means  of  modifying  the  oxygen  of  the  air. 

Returning  now  to  the  fact  that  the  slow  combus- 
tion of  phosphorus  throws  a  portion  of  the  surround- 
ing oxygen  into  a  peculiar  condition,  in  which  it  is 


OZONE.  117 


highly  active  in  producing  decay  and  other  processes 
of  oxidation, — it  certainly  seems  probable  that  decay 
and  respiration,  which  are  also  examples  of  slow 
combustion,  may  act  on  the  air  in  the  same  way. 
Moreover,  the  inference  that  ozone  is  the  active 
agent  in  these  processes  is  also  supported  by  the 
fact  that  it  is  always  present,  to  a  greater  or  less  ex- 
tent, in  the  atmosphere,  although,  at  most,  in  ex- 
ceedingly minute  quantities.  Ozone,  being  so  highly 
corrosive,  cannot  be  present  in  the  atmosphere  in 
perceptible  quantities  without  producing  important 
effects,  and  some  persons  have  thought  not  only  to 
refer  to  it  the  various  processes  of  slow  combustion, 
but  also  to  trace  a  connection  between  the  preva- 
lence of  various  contagious  diseases  and  the  excess 
or  deficiency  of  this  agent  in  the  air  of  the  infected 
district  ;  but  these  speculations  are  not  as  yet  based 
on  sufficient  evidence,  and  are  not  worthy  of  serious 
attention. 

Without,  however,  introducing  any  theories  not 
yet  fully  established  into  the  line  of  our  argument, 
this  much  is  clear.  Oxygen  gas  appears  in  nature  in 
three  conditions,  or  under  three  manifestations : — 
first,  entirely  passive,  as  in  the  great  mass  of  the 
air;  secondly,  partially  active,  in  the  processes  of 
decay  and  respiration  ;  thirdly,  highly  active,  in  the 
phenomena  of  combustion.  In  each  of  these  condi- 
tions its  properties  have  been  adjusted  with  infinite 
skill  and  delicacy,  on  the  one  hand  to  the  thermal 
and  electrical  conditions  of  the  globe,  and  on  the 
other,  to  the  constitution  of  man  and  of  all  organic 
nature. 


Il8  OZONE. 


Here  I  must  conclude  my  brief  sketch  of  this 
wonderful  element.  If  I  have  succeeded  in  impress- 
ing on  your  minds  some  of  its  more  characteristic 
qualities,  if,  above  all,  you  have  become  aware  how 
exactly  and  delicately  these  qualities  have  been  ad- 
justed in  the  scheme  of  creation,  and  if  you  have 
seen  how  the  smallest  permanent  change  would  dis- 
turb the  result, — this  is  all  that  I  could  hope.  It 
might  be  expected  that  the  element  with  which 
creative  power  built  up  the  greater  part  of  the  crust  of 
our  globe,  leaving  only  a  small  excess  to  constitute 
its  atmosphere,  would  furnish  abundant  evidence  of 
design,  and  how  fully  is  this  expectation  realized ! 
Would  that  I  might  present  to  you  the  evidence 
more  forcibly  !  But  it  is  possible  in  a  popular  lec- 
ture only  to  touch  at  some  of  the  more  striking 
points,  and  I  have  felt  all  the  time  like  a  school- 
boy at  play,  in  spring,  in  some  garden  rich  in  flowers, 
snatching  here  and  there  a  few  of  the  more  gaudy 
tulips,  which  had  fully  bloomed,  but  leaving  the 
beautiful  and  delicate  buds  all  unnoticed.  But  then 
these  buds  of  knowledge  will  blossom,  and,  when 
the  summer  comes,  will  bear  a  still  sweeter  testi- 
mony of  goodness  and  of  love. 


CHAPTER   V. 


TESTIMONY   OF  WATER. 


The  atmosphere,  as  you  will  remember,  consists 
mainly  of  two  permanent  and  elementary  gases  ; 
and  having  discussed  the  functions  of  its  active 
element,  oxygen,  it  would  seem  natural  to  consider 
next  the  offices  of  nitrogen,  that  most  singularly 
inert  gas,  which  constitutes  no  less  than  four-fifths 
of  its  whole  mass  ;  but  we  shall  understand  more 
clearly  the  complicated  relations  of  this  truly  won- 
derful substance,  associated  as  it  is  with  all  the 
higher  forms  of  corporeal  vitality,  after  we  are 
acquainted  with  two  of  the  remarkable  cycles  in 
nature,  in  which  the  water  and  carbonic  dioxide 
of  the  atmosphere  play  a  conspicuous  part.  It  is 
true  that  these  two  substances  are  very  variable 
constituents,  and  make  up  at  best  only  an  exceed- 
ingly small  fraction  of  the  whole  mass  of  the  air ; 
but  nevertheless,  they  discharge  functions  no  less 
important  than  those  of  oxygen  and  nitrogen,  and 
we  shall  find  that  they  are  equally  rich  in  illustra- 
tions of  the  wisdom  and  power  of  God. 

I  have  already  alluded  to  the  fact  that  the  most 
striking  illustrations  of  creative  wisdom  have  been 

119 


I20  GENERAL  DIFFUSION  OF  WATER. 

discovered  in  those  substances  which  are  the  most 
abundantly  distributed  through  nature,  and  which 
are  the  most  intimately  associated  with  man,  and  of 
no  substance  is  this  principle  more  remarkably  true 
than  it  is  of  water.  As  you  well  know,  water  is  the 
liquid  of  the  globe,  and,  if  we  except  certain  tran- 
sient products  of  volcanic  action,  it  is  the  only  liquid 
which  exists  naturally  on  its  surface.  Moreover,  it 
is  in  constant  circulation,  and,  like  the  blood  in  our 
bodies,  is  the  medium  through  which  nourishment 
is  conveyed  to  all  parts  of  organized  nature,  and  its 
life  sustained.  We  should  naturally  expect  that  a 
substance  filling  so  important  a  place  in  the  scheme 
of  creation  would  furnish  undoubted  evidences  of 
design,  and  it  will  be  my  object  in  the  present  lec- 
ture to  illustrate  a  few  of  the  more  striking  ex- 
amples of  adaptation  which  its  qualities  present, 
beginning  with  the  aeriform  condition  of  water  as 
it  exists  in  the  atmosphere. 

The  condition  of  the  atmosphere  of  aqueous  va- 
por, which  surrounds  the  globe,  differs  essentially 
from  that  of  the  more  permanent  gases  which  are 
simultaneously  present.  Oxygen  and  nitrogen  can- 
not be  reduced  to  liquids  even  by  the  intense  cold 
at  the  poles.  It  is  very  different  with  aqueous 
vapor.  The  slightest  reduction  of  temperature, 
when  the  air  is  saturated  with  moisture,  is  sufficient 
to  condense  a  portion  of  the  vapor  to  water,  and  to 
shower  it  on  the  earth  in  drops  of  rain.  On  the 
other  hand,  when  the  temperature  rises,  the  heat 
converts  more  water  into  vapor,  and  the  aqueous 
atmosphere   is   replenished.      Thus   it   is   that   the 


THE  AQUEOUS  CIRCULATION.  121 

atmosphere  of  aqueous  vapor  on  the  earth  is  liable 
to  very  great  fluctuations,  from  which  the  Creator 
has  protected  the  great  mass  of  the  air  by  endowing 
oxygen  and  nitrogen  with  the  power  of  retaining 
the  aeriform  condition  under  all  circumstances ;  and 
we  shall  find  that  the  fluctuation  in  the  one  case  is 
as  important  as  the  stability  in  the  other. 

I  stated  in  the  last  lecture  that  our  atmosphere 
may  be  regarded  as  made  up  of  three  partial  at- 
mospheres, simultaneously  surrounding  the  globe, 
and  as  was  the  case  with  the  atmosphere  of  oxygen, 
we  shall  best  understand  the  fluctuations  of  the 
aqueous  atmosphere  if  we  begin  by  eliminating,  for 
a  moment,  from  our  thoughts  the  other  two.  In 
order  to  make  the  subject  clear,  it  will  be  neces- 
sary for  me  to  dwell  very  briefly  on  a  few  well- 
established  facts  in  meteorology,  which,  although 
not  very  interesting  in  themselves,  will  unfold  to  us 
some  of  the  beautiful  provisions  of  nature  by  which 
the  aqueous  circulation  of  the  globe  is  maintained. 

If  there  were  no  free  oxygen  or  nitrogen  gas,  the 
earth  would  still  be  surrounded  with  an  atmosphere 
of  aqueous  vapor,  and  we  are  able  to  foresee,  in 
some  small  measure,  what  the  conditions  of  such  an 
atmosphere  would  be.  Its  density  at  the  sea  level 
would  depend  chiefly  on  the  temperature,  and 
would  therefore  vary  very  rapidly  with  the  latitude, 
and  would  be  constantly  changing  at  the  same  lo- 
cality with  the  alternations  of  the  climate.  We  are 
able  to  determine  approximately  what  the  density 
would  be  at  any  given  temperature,  and  a  few  of 
the  results  are  included  in  the  following  table : 

6 


122 


THE  AQUEOUS   CIRCULATION. 


Weight  at  the  Sea  Level  of  one  Cubic  Foot  of  Vapor. 


Temperature. 
Fahrenheit. 


Weight. 
Grains. 


o° 0.78 

10° I. II 

20° 1.58 

30° 2.21 


Temperature. 
Fahrenheit. 


40  . 

50°. 
60°. 


Weight. 
Grains. 

•     3.09 
.     4.28 

.     5.87 


Temperature. 
Fahrenheit. 


70     . 

8o^ 


90 


Weight. 
Grains. 

.     8.00 

.10.81 

.14.50 


It  is  evident  from  these  numbers,  that  a  very- 
small  change  of  temperature  would  cause  immense 
fluctuation  in  such  an  atmosphere.  At  0°  one 
cubic  foot  of  the  aqueous  atmosphere  could  contain 
only  about  three-fourths  of  a  grain  of  vapor,  while 
at  80°  it  could  contain  fifteen  times  as  much,  and 
hence,  although  under  the  tropics  the  density  of  our 
assumed  atmosphere  would  be  comparatively  large, 
there  would  be  almost  a  complete  vacuum  at  the 
poles.  Into  this  vacuum  the  vapor  would  flow  from 
the  equator,  and  thus  in  either  hemisphere  there 
would  result  a  perfect  torrent  of  vapor  rushing  to- 
wards the  North  or  South.  But  it  is  also  evident 
that,  as  this  current  became  chilled  in  passing 
through  the  cooler  climate  of  the  temperate  zone, 
the  vaporwould  gradually  condense  to  water,  which, 
falling  on  the  land  or  on  the  ocean,  would  return 
in  time  to  the  equator,  ready  to  begin  again  the 
same  succession  of  ceaseless  changes. 

Although  the  presence  of  the  air  materially  mod- 
ifies, it  does  not  essentially  change,  the  aqueous  cir- 
culation. The  air  retards  the  formation  of  vapor, 
but  does  not  prevent  it,  and  at  any  given  tempera- 
ture the  same  amount  of  water  will  evaporate  into 


THE  AQUEOUS   CIRCULATION.  I23 

a  given  space,  whether  it  be  a  perfect  vacuum  or 
filled  with  air.  Thus,  for  example,  when  air  at  80° 
is  saturated  with  moisture,  it  contains,  as  before,  ex- 
actly 10.81  grains  of  vapor,  and  the  table  just  given 
applies  equally  well  to  the  actual  condition  of  the 
globe,  covered  with  its  dense  atmosphere  of  oxygen 
and  nitrogen,  as  to  the  case  just  assumed.  There 
is,  however,  a  most  important  difference  between 
the  two  conditions,  —  a  difference  on  which  the 
adaptation  of  the  system  of  aqueous  circulation  in 
the  order  of  nature  entirely  rests. 

Were  there  no  air  on  the  globe,  the  quantity  of 
vapor  would  adjust  itself  almost  instantaneously  to 
any  variation  of  temperature,  and  the  maximum 
amount  possible  w^ould  always  be  present  at  any 
given  place.  An  elevation  of  temperature  would  be 
attended  by  rapid  evaporation,  and  the  amount  of 
water  required  to  fill  the  space  would  suddenly  flash 
into  vapor ;  while,  on  the  other  hand,  a  correspond- 
ing depression  of  temperature  would  be  accompa- 
nied with  an  equally  sudden  precipitation  of  the 
excess  of  water  which  the  air  could  no  longer  con- 
tain, not  in  genial  showers  or  diffusive  rain,  but  in 
terrific  torrents,  of  which  the  deluging  showers  of 
the  tropics  can  give  us  only  a  feeble  conception  ;  for 
the  drops,  falling  without  resistance,  would  be  as 
destructive  in  their  effects  as  volleys  of  leaden  shot. 

In  the  actual  condition  of  the  atmosphere,  the 
presence  of  a  dense  medium  very  greatly  retards 
these  changes,  and  although  it  does  not  alter  their 
essential  nature,  it  moderates  their  action  and  miti- 
gates the  violence  of  their  effects.     An  elevation  of 


124  THE  AQUEOUS   CIRCULATION. 

temperature  is  followed  by  an  evaporation  of  water 
into  the  air  ;  but  the  process  is  comparatively  slow, 
and  it  is  a  long  time  before  the  air  is  fully  saturated. 
So,  also,  when  the  air  is  saturated,  a  depression  of 
temperature  is  followed  by  the  condensation  of  a 
portion  of  the  vapor  into  rain ;  but  here,  again,  the 
mass  of  the  atmosphere  tempers  the  abruptness  of 
the  transition,  and  allays  its  violence.  The  vapor 
condenses  first  into  a  fine  dust  consisting  of  repellent 
particles  of  water,  which  are  so  minute,  and,  conse-^ 
quently,  fall  so  slowly  against  the  resistance  of  the 
air,  that  they  seem  to  float  in  the  atmosphere ;  and 
when,  in  consequence,  probably,  of  some  electrical 
discharge,  these  particles,  losing  repulsive  energy, 
unite  to  form  drops  of  rain,  they  again  are  wafted 
down  so  slowly  through  the  resisting  medium,  and 
alight  so  softly,  that  the  "  soft  falling  snow  and  the 
diffusive  rain  ''  have  become  fit  emblems  of  the  be- 
neficence of  God,  as  they  give  the  strongest  evi- 
dences of  his  wisdom  and  skill.  Moreover,  the  glori- 
ous clouds,  which  add  so  much  to  the  beauty  of  the 
landscape,  and  typify  in  their  virgin  whiteness  the 
purity  of  heaven,  are  only  collections  of  water  dust 
floating*  in  the  upper  atmosphere,  and  mark  the 

*  It  is  well  known  that  in  a  mass  of  air  charged  with  aqueous  vapor, 
the  tension  of  the  vapor  is  added  to  the  tension  of  the  air,  and  that 
such  a  mixture  is  lighter  than  a  mass  of  dry  air  of  the  same  tempera- 
ture, whose  tension  equals  the  united  tension  of  the  gas  and  vapor.  If, 
now,  the  vapor  in  such  a  mass  of  air  is  condensed  to  water  dust,  whose 
particles  are  mutually  repelled  by  their  similar  electrical  charges,  we 
may  conceive  that  the  electrical  tension  takes  the  place  of  the  tension 
of  the  vapor,  so  that  the  resulting  cloud,  as  a  whole,  may  be  as  light 
as  the  surrounding  atmosphere  in  which  it  floats. 


THE  AQUEOUS   CIRCULATION.  1 25 

stage  of  transition  between  vapor  and  rain  ;  and, 
further  still,  it  is  probable,  as  I  stated  in  a  previous 
lecture,  that  it  is  these  same  minute  liquid  drops 
which  tint  the  morning  and  evening  sky  with  their 
gorgeous  hues,  and  cover  our  earthly  dwelling-place 
with  its  canopy  of  blue. 

Again,  the  presence  of  the  air  very  greatly  re- 
tards the  aqueous  circulation  above  described,  with- 
out" altering  its  essential  character.  There  is  now 
the  same  great  difference  between  the  density  of 
the  atmosphere  of  vapor  at  different  latitudes,  as  if 
it  were  the  only  atmosphere  on  the  globe,  and  the 
dense  vapor  of  the  tropics  tends  constantly  to  flow 
towards  either  pole  ;  but  as  it  cannot  move  without 
carrying  with  it  the  whole  mass  of  the  atmosphere, 
this  tendency  merely  increases  the  velocity  of  those 
great  aerial  currents,  already  described  in  a  previous 
lecture.  Still  the  general  fact  remains  the  same. 
From  the  whole  surface  of  the  globe  water  is  con- 
stantly evaporating  into  the  aqueous  atmosphere 
which  surrounds  it.  The  heated  air  from  the  tropics, 
heavily  charged  with  moisture,  is  continually  mov- 
ing towards  the  colder  regions,  both  of  the  North 
and  of  the  South  ;  and  as  the  current  thus  becomes 
chilled,  the  vapor  is  slowly  condensed,  and  the  water 
showered  down  in  fertilizing  rains  on  the  land. 
Thus  it  is  that  those  beautiful  provisions  which  we 
see  in  the  rain  all  depend  on  the  presence  of  the  air, 
and  result  from  a  careful  adjustment  of  the  proper- 
ties of  aqueous  vapor  to  the  exact  density  of  our 
atmosphere.  "  Hath  the  rain  a  Father?  '*  Science, 
by  discovering  these  evidenceToT^skllTul  adaptation, 


126  THE  AQUEOUS   CIRCULATIOK 

has  most  conclusively  answered  this  question,  and 
the  answer  is  the  same  now  as  in  the  days  of  Job. 
"Behold,  God  is  great.  .  .  .  He  maketh  small  the 
drops  of  water:  they  pour  down  rain  according  to 
the  vapor  thereof." 

But  what  becomes  of  the  rain  ?  Would  that  I  could 
answer  this  question  satisfactorily.  We  all  under- 
stand the  general  theory  of  the  aqueous  circulation, 
but  the  deepest  philosophy  and  the  keenest  science 
are  not  able  to  fathom  its  details,  or  to  comprehend 
in  their  fulness  the  world  of  wonderful  adaptations 
which  the  question  unfolds.  We  all  know  that  the 
drops  of  rain  percolate  through  the  soil,  and  collect 
in  natural  reservoirs  formed  between  the  layers  of 
rock,  and  that  these  reservoirs  supply  the  springs. 
The  rills  from  numerous  adjacent  springs  unite  to 
form  a  brook,  which  increases  as  it  flows,  until  it 
finally  becomes  the  majestic  river,  rolling  silently  on 
its  course.  Every  drop  of  that  water  has  been  an 
incessant  wanderer  since  the  dawn  of  creation,  and 
it  will  soon  be  merged  again  in  the  vast  ocean,  only 
to  begin  anew  its  familiar  journey.  If  you  would 
gain  an  idea  of  the  magnitude  and  extent  of  this 
wonderful  circulation,  you  must  bring  together,  in 
imagination,  all  the  rivers  of  the  world,  the  Amazon 
and  the  Orinoco,  the  Nile  and  the  Ganges,  the  Mis- 
sissippi and  the  St.  Lawrence,  and,  adding  to  these 
the  ten  thousands  of  lesser  streams,  endeavor  to  form 
a  conception  of  the  incalculable  amount  of  water 
which  during  twenty-four  hours  they  pour  into  the 
vast  basin  of  the  world,  and  then  remember  that 
during  the  same  period  at  least  four  times  as  much 


THE   AQUEOUS   CIRCULATION.  I27 

water  must  have  been  raised  in  vapor,  and  scattered 
in  rain  over  the  surface  of  the  globe.  Would  you 
form  an  idea  of  the  importance  of  this  circulation, 
you  must  not  limit  your  appreciation  to  its  economi- 
cal value,  as  a  great  source  of  power,  working  the 
mills  and  the  forges  of  civilized  man,  and  building 
up  vast  marts  of  manufacturing  industry,  nor  must 
you  regard  alone  its  commercial  value,  bearing  as  it 
does  on  its  bosom  to  the  ocean  the  freights  of  em- 
pires. These  applications  of  power,  however  impor- 
tant in  themselves,  are  insignificant  in  extent  com- 
pared with  those  mighty  agencies  which  the  aque- 
ous circulation  is  constantly  exerting  in  nature.  It 
has  been  the  great  agent  of  geological  changes  :  here 
washing  avv^ay  continents,  and  there  building  them 
up ;  here  gullying  out  valleys,  and  there  smoothing 
away  inequalities  of  surface ;  here  dissolving  out  the 
particles  of  metals  from  the  solid  rocks,  and  there 
collecting  them  together  in  beds  of  useful  ores.  It 
has  covered  the  earth  with  verdure  and  animal  life, 
by  conveying  nourishment  to  the  plant  and  food  to 
the  animal.  It  sustains  our  own  bodies,  for  it  is  a 
portion  of  this  very  circulation  which  ebbs  and  flows 
in  our  veins,  and  whose  pulsations  beat  out  the  mo- 
ments of  our  lives  ;  and  could  I  bring  together  in  one 
picture  the  infinite  number  of  beneficent  ends  which 
it  has  been  made  by  Providence  to  subserve,  I  am 
sure  that  you  would  agree  with  me  that  there  is  not 
in  nature  stronger  evidence  of  design  than  in  the 
adaptations  of  this  simple  and  familiar  liquid. 

In  order  that  we  may  appreciate,  in  some  humble 
measure,  the  force  of  this  evidence,  let  us  consider 


128  ADAPTATION    OF    WATER. 

some  of  the  qualities  of  water;  but,  at  the  same 
time,  let  us  not  forget  that  the  strength  of  our 
argument  lies  not  so  much  in  the  fact  that  each 
property  has  been  skilfully  adjusted  to  some  spe- 
cific end,  as  it  does  in  the  harmonious  working  of 
all  the  separate  details.  Had  man  creative  power, 
the  first  would  fall  within  the  range  of  his   intelli- 

I  gence ;  but  to  adapt  the  same  substance  to  a  thou- 
sand different  ends,  and  to  adjust  each  of  its  prop- 
erties to  a  thousand  different  conditions,  covering 
with  their  complex  network  all  the  known  universe, 
implies  a  power  nothing  less  than  infinite,  and  an 

I  intelligence  nothing  lower  than  divine.  It  is  evi- 
dent,  however,  that  we  can  gain  a  knowledge  of  the 
general  plan  only  by  studying  the  details,  and  un- 
fortunately it  is  to  these  details  that  our  accurate 
knowledge  is  almost  entirely  confined.  We  can 
see,  for  example,  that  each  property  of  water  has 
been  designed  for  some  specific  purpose.  We  can 
also  recognize  the  evident  fact,  that  all  the  proper- 
ties work  harmoniously  together  in  the  general 
scheme  of  nature;  but,  in  the  present  state  of 
knowledge,  to  trace  the  intimate  relations  of  these 
properties  is  frequently  as  impossible  as  it  is  to 
form  a  clear  conception  of  the  coexistenee  and  har- 
monious action  of  all.  Yet  in  these  very  facts  lies 
the  whole  force  of  the  argument  from  design,  and  it 
is  only  the  limitations  of  our  knowledge  and  facul- 
ties which  weaken  the  impression  on  our  minds. 
But  were  these  limitations  removed,  all  argument 
would  become  unnecessary,  for  then,  reasoning 
would  be  exchanged  for  vision,  and  in  the  reful- 


A  CONSTITUENT   OF   ORGANIZED   BEINGS.      1 29 

gence  of  the  Divine  Presence  we  should  know  even 
as  we  are  known. 

It  is  a  familiar  fact,  that  water  is  an  essential  con- 
dition of  organic  life ;  but  few  persons,  I  suspect, 
are  aware  that  this  familiar  liquid  constitutes  the 
greater  part  of  all  organized  beings.  The  physical 
man  has  been  described  by  one  writer  as  consist- 
ing of  merely  a  few  pounds  of  solid  matter  dis- 
tributed through  six  pailfuls  of  water,  and  it  is  a 
fact  that  no  less  than  four-fifths  of  these  bodies  of 
ours  are  made  up  of  water.  Yet  this  is  a  small 
proportion  compared  with  the  amount  which  enters 
into  the  structure  of  most  of  the  lower  animals. 
Some  of  these,  such  as  the  medusae, — sunfishes, — are 
little  else  than  organized  water.  Professor  Agassiz 
obtained  from  one  of  the  large  sunfishes  found  on 
our  coast,  weighing  thirty  pounds,  only  two  hundred 
and  forty  grains  of  solid  matter ;  and  we  may  safely 
say  that  at  least  nine  hundred  and  ninety-nine  parts 
in  a  thousand  of  these  singular  animals  consist  of 
water.  Water  constitutes,  to  almost  as  great  an  ex- 
tent, most  of  the  vegetable  products  which  are  articles 
of  food,  as  will  be  seen  by  the  accompanying  table. 


Plums 

contaii] 

L  75  per  cent,  of  water. 

Potatoes 

75 

Apples 

80 

Carrots 

^3 

Turnips 

90 

Watermelons 

94 

Cucumbers 

97 

It  is  evident  from  these  facts  that  water  is  the 

6* 


I30     A   CONSTITUENT  OF  ORGANIZED   BEINGS. 

chief  material  of  which  all  organized  structures  are 
formed,  and  in  studying  the  aqueous  circulation  we 
have  already  become  acquainted  with  the  beautiful 
provisions  of  nature  by  which  this  life-giving  liquid 
is  distributed  over  the  earth,  and  showered  down 
upon  the  meadow  and  forest  alike.  Without  water 
organic  life  cannot  exist,  and  where,  from  any  local 
causes,  the  supply  fails,  there  we  find  a  barren  wil- 
derness;  while,  on  the  other  hand,  the  genial  influ- 
ences of  the  rain  will  soon  make  even  "  the  desert 
blossom  as  the  rose."  It  is  a  remarkable  fact  of 
physical  geography,  that  the  distribution  of  water  by 
the  aqueous  circulation  is  rendered  more  effective 
by  the  peculiar  structure  of  the  continents,  and  the 
position  of  the  great  mountain  chains. 

**The  mountain  chains,"  writes  Professor  Guyot, 
in  his  excellent  work  Earth  and  Man^  "  are  great 
condensers,  placed  here  and  there  along  the  con- 
tinents to  rob  the  winds  of  their  treasures,  and  to 
serve  as  reservoirs  for  the  rain-waters,  and  to  dis- 
tribute them  afterwards  as  they  are  needed  over  the 
surrounding  plains.  Their  wet  and  cloudy  summits 
are  untiringly  occupied  with  this  important  work, 
and  from  their  sides  flow  numberless  torrents  and 
rivers,  carrying  in  all  directions  wealth  and  life." 

Thus  the  mountains,  whose  majestic  forms  affect 
so  powerfully  the  human  soul,  and  which  have  ex- 
erted such  an  influence  on  the  history  of  the  race, 
are  also  among  the  most  beneficent  means  in  the 
Divine  Providence  by  which  the  earth  has  been  fer- 
tilized and  rendered  a  fit  abode  for  man.  Moreover, 
these  mountain  chains  have  been  evidently  so  dis- 


THE  DEW.  131 


tributed  as  to  give  the  greatest  efficiency  to  the 
aqueous  circulation,  and  to  irrigate  the  continents 
most  effectively  with  their  fertilizing  floods.  We 
cannot,  therefore,  suppose  that  even  these  ridges  on 
the  earth's  surface,  which  are  the  lasting  records  of 
ancient  geological  changes,  were  fixed  by  chance, 
for  they  also  bear  traces  of  His  intelligence  who 
seeth  the  end  from  the  beginning,  and  every  part 
of  whose  works  is  adapted  to  every  other.  "  Lord, 
thou  hast  been  our  dwelling-place  in  all  generations. 
Before  the  mountains  were  brought  forth,  or  ever 
thou  hadst  formed  the  earth  and  the  world,  even 
from  everlasting  to  everlasting,  thou  art  God." 

But  it  is  not  the  mountains  alone  which  condense 
the  vapor  of  the  atmosphere ;  for,  under  certain 
conditions,  the  level  plains  act  in  a  similar  way,  and 
distil  the  precious  drops  of  dew  upon"  field  and 
meadow,  distributing  it  among  the  plants  with  dis- 
criminating care  for  the  necessities  of  each.  The 
dew  is  simply  another  phase  of  the  great  aqueous 
circulation,  and,  like  the  rain,  it  is  a  persuasive  wit- 
ness of  the  Divine  Disposer,  who  has  adjusted  its 
amount  to  the  wants  of  the  vegetable  world.  Every 
one  has  noticed  the  deposition  of  moisture  on  a 
pitcher  of  ice-cold  water  during  a  summer's  day, 
and  in  this  familiar  fact,  we  have  at  once  an  example 
and  an  illustration  of  the  simple  provision  by  which, 
during  even  the  long  droughts  of  summer,  the  plants 
receive  a  partial  supply  of  water,  sufficient,  at  least, 
to  sustain  their  life  until  the  later  rains  bring  the 
autumn  fruits  to  maturity,  and  stimulate  a  more 
vigorous  growth. 


132  THE    DEW. 


The  explanation  of  the  dew  upon  the  pitcher  is 
very  simple.  The  layer  of  air  in  contact  with  its 
cold  mass  is  rapidly  cooled,  and  when  it  can  no 
longer  hold  all  the  moisture  it  contains,  the  excess 
is  deposited  in  drops  on  the  surface.  Exchange 
now  the  pitcher  for  the  earth,  and  you  have  at  once 
an  explanation  of  the  proximate  cause  of  the  dew. 
After  sunset  the  earth,  like  the  pitcher,  cools  down 
the  layer  of  atmosphere  immediately  in  contact  with 
it  to  such  a  degree  that  the  whole  of  the  vapor  can 
no  longer  retain  its  aeriform  condition.  As  a  neces- 
sary result,  a  portion  is  condensed  and  deposited 
upon  the  surface,  and  this  is  what  we  call  dew.  But  it 
will  be  asked.  What  cools  the  earth  so  suddenly  after 
the  setting  of  the  sun  ?  For  this  is  not  so  evident  as 
the  cause  of  the  coldness  of  the  pitcher.  Certainly 
not,  and  the  question  will  lead  us  to  a  study  of  those 
relations  in  which  the  adaptations  to  be  discovered 
in  this  natural  phenomenon  are  chiefly  to  be  found. 

The  earth,  as  I  stated  in  the  second  lecture,  is 
moving  with  immense  rapidity  through  a  space 
whose  temperature  is  at  least  270  degrees  below  the 
zero  of  Fahrenheit's  thermometer,  and,  like  a  heated 
cannon-ball  hung  in  the  middle  of  a  cold  room,  it  is 
continually  losing  heat  by  radiation.  The  dense 
atmosphere  with  which  it  is  enveloped,  acting,  as  we 
have  seen,  like  a  blanket,  protects  the  earth  from  the 
intense  cold  of  space  to  a  certain  extent ;  but  still 
the  constant  loss  of  heat  is  so  great,  that,  were  the 
sun's  rays  withheld  for  a  few  days,  the  temperature 
of  the  surface-land,  even  in  the  tropics,  would  fall  as 
low  as  it  is  now  at  the  poles  during  the  long  night 


THE   DEW.  133 


of  the  arctic  winter.  In  the  daytime  the  earth  re- 
ceives from  the  sun  more  heat  than  it  loses ;  but 
when  this  great  thermal  source  is  temporarily  with- 
drawn, the  loss  of  heat  continuing  as  rapidly  as  be- 
fore, the  surface  becomes  quickly  cooled,  and  the 
deposition  of  dew  follows,  as  just  explained  ;  or,  if 
the  temperature  falls  below  the  freezing-point,  the 
dew  is  changed  to  frost. 

You  must  all  have  noticed  that  the  most  copious 
deposition  both  of  dew  and  frost  takes  place  on  clear 
nights,  and  that  during  cloudy  weather  this  supply 
of  moisture  is  entirely  withheld.     The  reason  is  ob-  i 
vious.     The  earth  loses  heat  by  radiation,  and  the  j 
clouds,  intercepting  the  rays,  reflect  them  back  to  f 
the  earth.     A  shed  or  any  other  protection  spread 
over  the  ground  acts  in  the  same  way,  and  it  is  well 
known  that  a  covering,  however  slight,*  is  sufficient 
to  protect  tender  plants  from  the  blight  of  the  early 
frosts.     Can  it  then  be  an  accident,  a  mere  result  of 
chance,  that  the  dew  is  deposited  most  abundantly 
where  it  is  needed  most,  and  that  this  supply  of 
moisture  fails  only  when  the  clouds  promise  a  more 
copious  draught  of  liquid  nourishment  from  the  rain  ? 

There  is  still  another  fact  presented  by  the  dew 
which  is  equally  suggestive.  The  heavens  do  not 
distil  their  liquid  treasures  upon  all  objects  alike, 
but  the  dew  is  deposited  much  more  abundantly 
on  the  herbage,  the  shrubs,  and  the  trees,  which 
need  the  refreshing  moisture,  than  on  fallow  land, 
the  sandy  plain,  or  the  beaten  road  ;  and  here 
again  the  cause  has  been  discovered.  It  is  evident 
from  the   general  theory  of  the  subject,  that   the 


134  THE    DEW. 


largest  amount  of  dew  will  fall  on  the  coldest  surface, 
and  it  is  equally  obvious  that,  other  things  being 
equal,  those  objects  will  cool  most  rapidly  which 
have  the  smallest  supply  of  heat  to  lose,  and  which 
radiate  it  with  the  greatest  freedom.  Now  it  has 
been  ascertained  by  experiment,  that  the  facility  of 
radiating  heat  depends  entirely  on  the  nature  of  the 
surface,  and  the  surfaces  of  leaves  have  such  a  re- 
markable power  in  this  respect,  that  it  would  seem 
as  if  they  were  especially  designed  for  the  purpose. 
If  next  you  consider  how  small  a  quantity  of  matter 
the  leaves  contain,  compared  with  their  large  radi- 
ating surfaces,  you  will  see  that  there  are  all  the 
conditions  present  of  rapid  cooling.  When,  there- 
fore, under  a  clear  evening  sky;  the  rays  of  heat  are 
escaping  from  all  objects  into  the  celestial  space,  the 
green  foliage  soon  becomes  colder  than  the  barren 
rocks  or  the  inanimate  clod,  and  receives,  in  conse- 
quence, a  greater  supply  of  dew. 

It  will  be  remembered,  as  I  stated  in  the  second 
lecture  of  this  course,  that  the  points  of  leaves  have 
the  power  of  silently  discharging  the  thunderbolts 
of  heaven,  and  that,  in  consequence,  every  tree  acts 
far  more  efficiently  to  avert  the  stroke  of  this  destruc- 
tive agent  than  the  best  constructed  lightning-rod. 
Is  not,  now,  the  force  of  this  evidence  of  adaptation 
very  greatly  enhanced,  when  we  find  that  the  sur- 
faces of  these  same  leaves  have  been  endowed  with 
an  equally  remarkable  power  of  radiating  heat,  by 
which  they  are  insured  a  daily  supply  of  moisture 
when  they  need  it  most  ?  Could  the  adaptation  of 
the  structure  of  the  leaf  to  these  two  entirely  dis- 


THE   DEW.  135 


tinct  physical  conditions  of  the  atmosphere  be  the 
result  of  anything  but  intelligence  ?  Admitting,  with 
the  modern  advocates  of  the  development  theory, 
that  under  the  pressure  of  circumstances  a  plant 
may  change  its  structure  so  as  to  adapt  it  to  the 
external  conditions,  still  I  think  no  one  will  be  so 
bold  as  to  maintain  that  there  can  be  any  brute 
agency  in  vegetation  endowed  with  such  foresight 
as  to  have  adapted  the  material  and  structure  of 
each  leaf,  from  the  very  first,  to  the  physical  condi- 
tions of  the  globe,  and  this,  moreover,  for  the  pur- 
pose of  effecting  ends  so  remotely  connected  with 
its  own  organization  as  the  discharge  of  electricity 
or  the  radiation  of  heat.  If  this  can  result  from 
chance,  under  its  modern  name  of  natural  selection, 
then  chance  is  but  a  counterfeit  name  of  God. 
Gideon  believed  that  God  would  save*  Israel,  be- 
cause the  dew  fell  on  the  fleece,  but  not  on  the 
ground,  and  afterwards  on  the  ground,  but  not  on 
the  fleece;  and  shall  we  doubt  the  reality  of  the 
Divine  Providence,  before  whom  a  similar  miracle 
is  repeated  every  evening,  with  such  beneficent  re- 
sults? If  it  be  the  mark  of  intelligence  to  be  able 
to  fathom  and  comprehend  this  wonder  of  Nature, 
can  it  be  anything  below  Infinite  Intelligence  ^^  who 
hath  begotten  the  drops  of  dew  "  ? 

I  might,  with  advantage,  enter  more  into  detail  in 
regard  to  the  laws  of  the  distribution  both  of  the 
rain  and  of  the  dew,  but  time  and  space  forbid.  I 
have  been  able  only  to  open  the  subject ;  yet  if  I 
have  succeeded  in  impressing  you  with  the  extent 
of  the  field  which  these  beautiful  phenomena  pre- 


136  WATER  THE   GREAT  PURIFIER. 

sent  to  your  inquiry,  it  is  all  that  I  could  expect. 
We  have  seen  that  it  is  through  these  familiar  chan- 
nels that  liquid  nourishment  is  conveyed  to  the  or- 
ganic world,  and  the  reservoirs  supplied  which  feed 
the  great  river-system  of  the  globe.  But  we  should 
form  a  very  imperfect  idea  of  the  resources  of  nature 
were  we  to  limit  our  regards  of  the  aqueous  circula- 
tion to  this  important  use.  The  life-blood  of  our 
bodies,  which  conveys  to  each  muscle  the  nourish- 
ment it  requires,  when  it  returns  again  through  the 
veins,  this  errand  well  done,  is  no  less  usefully  em- 
ployed in  carrying  away  the  portions  of  the  tissues 
which  have  been  worn  out  in  the  processes  of  life  ; 
and  where  from  any  cause  this  last  function  is  not 
faithfully  discharged,  and  the  wasted  muscles  are 
allowed  to  remain  in  the  system,  disease  and  death 
are  the  inevitable  results.  So  also  is  it  with  the  life- 
liquid  of  nature,  which  in  the  rain  and  the  dew  car- 
ries food  to  the  whole  organic  world.  When  this 
office  has  been  fulfilled,  it  returns  again  to  the  ocean, 
washing  away  those  waste  products  of  organic  life, 
which,  if  they  remained,  would  cause  pestilence 
and  death.  It  is  true  that  we  cannot  trace  all 
the  details  of  this  cleansing  process  ;  but  you  need 
not  the  aid  of  science  to  assure  you  of  the  general 
facts.  Let  the  free  flowing  of  the  rain-water  be 
interrupted,  and  you  well  know  that  stagnant  pools, 
breeding  pestilence,  or  deadly  swamps,  exhaling  ma- 
laria, are  the  immediate  results.  I  cannot  overstate 
the  importance  of  this  function  of  the  aqueous  cir- 
culation, or  too  strongly  insist  on  the  evidence  of 
wisdom  which  the  adaptation  of  the  properties  of 


^ESTHETIC  ASPECTS.  1 37 

water  to  this  beneficent  end  implies.  It  is  the 
great  cleansing  agent  of  the  world.  Wherever  it 
flows,  there  it  purifies,  and  its  limpid  streams,  clear 
as  crystal,  are  fit  emblems  of  the  purity  of  heaven. 
Hence  the  significance  of  this  liquid  in  all  religious 
systems.  The  ancient  Egyptians  worshipped  the 
water  of  the  Nile,  and  the  Hindoo  idolaters  of  the 
present  day  reverence  with  equal  devotion  the  wa- 
ter of  the  Ganges.  Passing  to  Judaism,  we  find  the 
washing  with  water  enjoined  as  a  sacred  duty  by 
the  Hebrew  law  ;  and  lastly,  in  the  Christian  dis- 
pensation the  pure  liquid  has  become  the  medium 
of  its  most  sacred  rite,  and  the  outward  washing  of 
baptism  typifies  that  inward  "  washing  of  regenera- 
tion," by  which  alone  man  is  saved. 

Glancing  now,  for  a  single  moment,  at  the  aesthetic 
aspects  of  the  subject,  consider  what  sources  of 
pleasure  the  varied  phases  of  the  aqueous  circula- 
tion furnish,  and  what  an  influence  on  the  soul  of 
man  they  are  calculated  to  exert.  The  bubbling 
spring,  the  purling  rill,  the  murmuring  brook,  the 
sparkling  cascade,  the  roaring  torrent,  the  majesti- 
cally flowing  river,  are  familiar  images  of  poetry, 
and  the  occasions  of  mental  emotions  which  all  have 
experienced  and  none  can  fully  describe ;  while  the 
mighty  cataract  and  the  ocean-storm  are  among  the 
sublimest  aspects  of  nature,  and  inspire  the  beholder 
with  reverence  and  awe.  When,  now,  you  reflect 
that  the  chords  of  the  human  soul  have  been  so 
strung  as  to  vibrate  in  sympathy  with  these  emo- 
tions of  the  material  creation,  and  that  thus  the 
aqueous  circulation  has  been  made  a  means  of  in- 


138  FERTILITY   OF  RESOURCES. 

structing  and  elevating  the  human  race,  can  you 
refuse  to  accept  the  evidence  of  wisdom  and  good- 
ness which  a  system,  so  far-seeing  in  its  design,  and 
so  beneficent  in  its  results,  affords  ? 

The  mechanism  of  nature  differs,  as  we  have  seen, 
from  the  creations  of  human  ingenuity,  in  the  fer- 
tility of  its  resources.  Man  combines  numerous 
means  in  order  to  produce  a  single  end;  but  in 
nature  the  most  varied  and  apparently  incompatible 
results  flow  from  a  single  design.  In  God's  works 
the  means  are  employed,  not  as  we  use  them  in  the 
poverty  of  our  resources,  but  from  the  exuberance 
of  riches.  To  use  the  language  of  another :  ^^  All 
the  means  are  ends,  and  all  the  ends  are  means ;  *' 
and  the  grand  result  is  an  harmonious  system,  in 
which  every  part  is  a  whole,  and  where  the  whole 
that  is  known  is  felt  to  be  only  a  very  insignificant 
part.  Such  is  the  character  of  the  aqueous  circula- 
tion, which  we  are  now  studying,  and  assuredly  the 
numerous  results  we  have  already  seen  flowing  from 
this  simple  mechanism  are  suf^cient  to  mark  the 
system  as  Divine  ;  but  we  have  not  as  yet  exhausted 
its  resources.  Indeed,  we  have  been  all  the  time 
looking  at  only  one  side  of  the  design,  and  there  is 
a  whole  set  of  adaptations  yet  unnoticed,  which  are 
no  less  important  in  the  scheme  of  organic  nature 
than  the  one  we  have  chiefly  considered.  And  when 
we  have  become  acquainted  with  these,  we  shall 
find  still  other  phases  of  this  boundless  plan  pre- 
sented to  our  view,  and  not  until  man  ceases  to 
learn  by  study,  or  the  waters  cease  to  roll,  will  the 
subject  be  exhausted. 


LATENT  HEAT  OF  STEAM.  1 39 

We  have  thus  far  only  considered  the  agency  of 
the  aqueous  circulation  in  distributing  over  the  earth 
the  chief  constituent  of  all  organic  matter,  together 
with  some  of  the  secondary  ends  which  the  river- 
system  of  the  globe  subserves.  But  there  is  another 
condition  of  organic  life  no  less  essential  than  moist- 
ure. The  animal  kingdom  is  absolutely  dependent 
on  the  vegetable,  and  plants  cannot  grow  except 
within  a  limited  range  of  temperature.  Therefore, 
unless  during  at  least  a  portion  of  the  year  the 
amount  of  heat  supplied  is  sufficient  to  maintain 
the  temperature  of  the  climate  within  the  required 
limits,  organic  life  cannot  exist  in  that  region.  Now 
this  familiar  substance,  water,  has  been  endowed 
with  most  remarkable  and  unusual  properties,  by 
which  the  aqueous  circulation  has  been  made  a  great 
means  of  distributing  heat,  and  thus  of  sustaining 
organic  life  in  vast  tracts  of  country  where  otherwise 
it  could  not  exist ;  and  it  is  to  this  class  of  its  adap- 
tations that  I  wish  next  to  call  your  attention. 

One  of  the  prominent  inventions  of  modern  times 
is  the  method  of  heating  large  buildings  by  steam. 
You  must  all  have  seen  the  apparatus.  There  is  first 
the  boiler,  where  the  steam  is  generated  by  the  com- 
bustion of  fuel ;  then  pipes,  by  which  it  is  distrib- 
uted to  the  different  rooms ;  next  the  iron  radiators, 
in  which  the  steam  is  condensed  to  water,  and  during 
this  change  gives  out  heat,  which  is  radiated  from 
the  corrugated  surface  of  the  iron;  and,  lastly,  the 
return  pipes,  through  which  the  condensed  water 
flows  back  to  the  boiler,  ready  to  start  again  on  the 
same   journey.     Every  one   is   familiar  with  these 


I40  HEATING  BY   STEAM. 

external  aspects  of  the  apparatus ;  but  all  may  not 
know  that  the  efficiency  of  the  method  depends 
entirely  upon  a  remarkable  quality  of  water,  a  qual- 
ity which  is  not  possessed  to  the  same  degree  by  any 
other  known  liquid.  Were  you  to  test  with  a  ther- 
mometer the  temperature  of  the  w^ater  in  the  boiler 
and  that  of  the  steam  rising  from  it,  you  would  be 
surprised  to  find, — if  you  were  not  forewarned  of  the 
fact, — that  they  were  precisely  at  the  same  point ; 
and  yet  in  order  to  change  one  pound  of  boiling 
water  into  one  pound  of  steam  it  is  necessary  to 
burn  up  sufficient  coal  to  raise  the  temperature  of 
ten  pounds  of  ice-cold  water  to  the  boiling-point. 
The  coal  which  is  burning  under  the  boiler  does  not 
raise  the  temperature  of  the  water.  Press  the  fire 
ever  so  hard,  you  cannot  increase  the  temperature 
either  of  the  water  or  of  the  steam  by  a  single  de- 
gree. The  effect  of  increasing  the  fire  will  be  only 
to  generate  steam  more  rapidly,  for  the  whole  of 
the  immense  amount  of  heat  set  free  by  the  burning 
fuel  is  absorbed  by  the  boiling  water  in  changing 
into  steam.  But  this  heat  is  not  lost.  It  reaaains 
latent^ in  the  steam,  is  carried  by  it  into  the  different 
rooms,  and  there,  when  the  steam  changes  back 
again  into  water,  it  is  all  given  up,  without  the 
slightest  diminution,  diffusing  its  genial  warmth 
through  the  house.  The  steam,  therefore,  is  merely 
the  vehicle  by  which  heat  is  carried  over  the  build- 
ing. The  heat  comes  from  the  burning  fuel  in  the 
cellar,  and  originally  it  came  from  the  sun ;  for  the 
coals  burning  under  the  boiler  are  merely  fagots,  as 
it  were,  of  condensed  sunbeams,  gathered  by  the 


THE   EARTHS   STEAM   HEATER.        -'         I4I  ^> 

plants  of  some  ancient  geological  epoch,  subse- 
quently fossilized  and  preserved  in  the  earth  for  our 
use.  The  steam  merely  acts  the  part  of  a  common 
carrier;  but  what  I  wish  you  to  notice  is  the  fact 
that  steam  is  peculiarly  fitted  for  the  work,  because 
it  has  been  made  capable  of  holding  so  large  a  quan- 
tity of  heat. 

Your  attention,  perhaps,  has  been  called  to  the 
efficiency  and  economy  of  this  method  of  heating; 
you  have  admired  its  neatness  and  absolute  safety 
from  fire,  and  have  been  delighted  with  the  softness  of 
the  temperature  which  it  diffuses  through  the  rooms; 
or,  if  you  have  examined  more  closely  the  details 
of  the  apparatus,  you  must  have  been  struck  with 
the  ingenuity  of  the  adjustments  by  which  it  is  self- 
regulated.  Yet  this  is  no  new  invention.  A  similar 
apparatus,  on  a  vastly  grander  scale,  working  with 
far  greater  economy  and  efficiency,  and  provided 
with  adjustments  of  wonderful  delicacy,  which  per- 
fectly regulate  its  action,  and  which  never  fail  and 
never  wear  out,  has  been  at  work  ever  since  the 
dawn  of  the  creation,  and  is  at  this  moment  soften- 
ing the  inclemency  of  our  northern  winter. 

The  general  aqueous  circulation  is  a  great  steam- 
heating  apparatus,  with  its  boiler  in  the  tropics  and 
its  condensers  all  over  the  globe.  The  sun's  rays 
make  the  steam,  and  wherever  dew,  rain,  or  snow 
falls,  there  the  heat,  which  came  originally  from  the 
sun,  and  which  has  been  brought  from  the  tropics 
concealed  in  the  folds  of  the  vapor,  is  set  free  to 
warm  the  less  favored  regions  of  the  earth.  This 
apparatus  of  nature,  although  so  much  simpler,  and 


142  THE   EARTH  S   STEAM   HEATER. 

working  without  pipes,  iron  boiler,  or  radiators,  is 
exactly  the  same  in  principle  as  the  steam-heater, 
which  may  be  seen  at  work  in  almost  every  large 
factor}-'.  It  is  true  that  the  atmospheric  vapor  is  a 
much  better  vehicle  of  heat  than  ordinary  steam,  and 
it  is  also  true  that  this  thermal  application  is  but 
one  of  the  hundred  uses  of  the  aqueous  circulation  ; 
but  still  the  general  method  is  the  same,  and  both 
systems  owe  their  efficiency  to  the  unique  property 
with  which  water  has  been  endowed.  It  is  true  that 
other  liquids  in  changing  into  vapor  absorb  heat, 
but  the  heat  stored  up  in  these  vapors  is  vastly  less 
than  that  in  steam,  and  it  must  be  noticed  that,  of 
all  created  forms  of  matter,  this  familiar  liquid,  which 
fills  the  ocean,  which  distils  upon  us  in  the  rain,  and 
which  flows  in  the  rivers,  is  the  only  substance 
which  has  been  thus  especially  endowed.  Is  this  an 
accidental  concurrence  of  circumstances?  or  is  it,  on 
the  contrary,  the  work  of  Infinite  Wisdom?  We 
regard,  and  with  reason,  the  beautiful  invention  of 
man,  by  which  our  dwellings  are  warmed,  as  an  evi- 
dence of  .intelligence  ;  and  can  we  refuse  to  recog- 
nize the  existence  of  that  higher  Intelligence,  which 
not  only  adjusted  the  more  perfect  system  of  nature, 
but  also  created  the  properties  of  water,  on  which 
the  efficiency  of  both  depends  ? 

Having  considered  that  peculiar  quality  of  vapor 
through  which  the  aqueous  circulation  becomes  an 
important  means  of  distributing  the  sun's  heat  over 
the  surface  of  the  globe,  we  might  next  discuss  more 
at  length  the  extent  of  its  influence,  and  examine  in 
detail  the  ingenious  system  of  checks  and  balances 


CAPACITY   OF  WATER  FOR  HEAT.  I43 

by  which  the  action  of  this  great  heating  apparatus 
is  regulated,  and  its  constant  working  secured  ;  but 
here,  as  before,  having  glanced  at  the  main  points, 
I  must  leave  it  to  your  study  to  fill  the  unavoidable 
blanks,  and  pass  on  to  consider  another  special 
property  of  water  by  which  a  similar  result  is  se- 
cured. 

The  amount  of  heat  required  to  raise  the  tem- 
perature of  a  pound  of  water,  or  of  any  other  sub- 
stance, one  degree,  is  capable  of  exact  measurement, 
and  the  quantity  has  been  determined  experimen- 
tally for  almost  every  known  substance.  These  ex- 
periments have  led  to  a  remarkable  result,  to  which 
I  alluded  in  a  former  lecture.  It  appears  that, 
when  water  is  heated  through  a  given  number  of 
degrees,  it  absorbs  more  than  twice  as  much  heat  as 
any  other  substance  (except  one  or  two  very  closely 
related  bodies),  and  more  than  ten  times  as  much  as 
iron  and  most  of  the  metals.  It  is  not  probable 
that  many  of  my  audience  have  verified  this  strik- 
ing result,  but  you  all  know  how  long  it  takes  to 
boil  a  tea-kettle,  even  over  a  brisk  fire,  and  have, 
therefore,  some  conception  of  the  amount  of  heat 
which  cold  water  is  capable  of  absorbing.  This 
familiar  experience  shows  that  water  has  a  very 
great  capacity  of  holding  heat,  and  accurate  ex- 
periment has  proved,  as  just  stated,  that,  with  the 
exception  just  noticed,  water  contains,  at  the  same 
temperature,  more  than  twice  as  much  heat  as  any 
other  solid  or  liquid  known. 

The  importance  of  this  simple  provision  will  ap- 
pear if   you    reflect  that   it  makes  the   ponds,  the 


144     THE  OCEANS  ARE  RESERVOIRS   OF  HEAT. 

lakes,  and  the  oceans  great  reservoirs  of  heat.  It 
not  only  requires  a  vast  amount  of  heat  to  warm 
one  of  these  large  bodies  of  water,  but  when  once 
warmed  they  cool  very  slowly.  Hence  the  marked 
difference  between  the  oceanic  and  the  continental 
climate  in  the  same  latitude.  During  the  summer 
the  ocean  eagerly  absorbs  the  heat  of  the  sun's  rays, 
which  are  showered  upon  it  in  such  profusion  ;  but 
water  has  so  great  a  capacity  for  heat,  that  the 
ocean,  nevertheless,  does  not  grow  very  warm,  and, 
moreover,  a  large  amount  of  the  heat  it  receives  is 
carried  away  by  the  vapor  which  is  constantly  rising 
from  its  surface.  In  winter,  on  the  other  hand,  the 
water  gives  up  its  heat  to  warm  the  colder  air  ;  but 
it  contains  such  an  inexhaustible  supply,  that  the 
loss  does  not  materially  lower  its  temperature. 
There  results,  in  consequence,  a  great  uniformity  of 
temperature,  in  which  the  air,  by  its  perpetual  con- 
tact with  the  surface  of  the  water,  necessarily  shares, 
and  this  uniformity  extends,  in  a  greater  or  less  de- 
gree, to  the -climate  of  all  islands  and  seaboard  dis- 
tricts. It  is  quite  different  with  the  surface  of  con- 
tinents. There  the  soil  becomes  rapidly  heated 
under  the  vertical  rays  of  a  summer's  sun,  and,  as 
its  particles  are  immovable,  the  surface-layer  soon 
rises  to  a  high  temperature ;  while,  on  the  other 
hand,  in  winter  it  is  cooled  by  radiation  with  equal 
rapidity ;  and  this  is  the  cause  of  those  extremes  of 
heat  and  cold  which  characterize  all  countries  of  the 
temperate  zone  removed  from  the  influence  of  the 
ocean.  The  oceanic  climate  is  moderate,  while  the 
continental  climate  is  excessive.     During  the  day, 


OCEANIC   AND    CONTINENTAL   CLIMATES.        I45 

under  the  same  circumstances,  the  land  is  warmer 
than  the  sea,  and  colder  during  the  night,  or,  taking 
the  different  seasons,  the  land  is  warmer  than  the 
sea  in  summer  and  colder  in  winter.  These  general 
principles  have  been  verified  by  the  extensive  series 
of  meteorological  observations  which,  during  the  last 
twenty-five  years,  have  been  made  all  over  the  civil- 
ized world.  You  will  find  an  excellent  abstract  of 
the  results  in  Professor  Guyot's  work  on  Earth  and 
Man,  before  referred  to.  I  have  time  only  to  cite 
a  few  familiar  facts  in  illustration  of  my  subject, 
which  I  will  give  nearly  in  his  words. 

**  On  the  coast  of  Cornwall  shrubs  as  delicate  as 
the  laurel  or  the  camellia  are  green  through  the 
whole  year,  while  under  the  same  latitude  in  the 
interior  of  the  continents,  the  most  hardy  trees  can 
alone  brave  the  rigor  of  the  winter.  But  on  the 
other  hand,  the  mild  climate  of  England  cannot 
ripen  the  grape,  although  almost  under  the  same 
parallel  grow  the  delicious  wines  of  the  Rhine.  At 
Astrachan,  on  the  northern  shore  of  the  Caspian,  as 
Humboldt  tells  us,  the  grapes  and  fruits  of  every 
kind  are  as  beautiful  and  luscious  as  in  the  Canaries 
and  in  Italy;  the  wines  have  all  the  fire  of  those  of 
the  south  of  Europe,  although  in  the  same  latitude, 
at  the  mouth  of  the  Loire,  on  the  Atlantic  sea-coast, 
the  vines  hardly  flourish  at  all.  But  while  in  the 
south  of  France  the  winter  is  a  perpetual  spring,  the 
summers  of  the  Caspian  are  succeeded  by  a  winter 
of  almost  polar  severity." 

I  might  multiply  illustrations,  but  these  are  sufB- 
cient  to  show  how  the  remarkable  property  of  water 
7 


146  EFFECT   OF   OCEAN   CURRENTS. 

which  we  are  considering  tends  to  equaHze  the  cli- 
mate of  the  globe. 

This  influence  of  water  is  very  greatly  increased 
by  the  oceanic  currents,  which,  like  the  winds,  are 
set  in  motion  by  the  heat  of  the  sun,  and  are  con- 
stantly carrying  the  warm  waters  of  the  tropics 
toward  the  poles.  One  of  the  most  remarkable  of 
these  currents  is  the  Gulf-Stream,  which  flows  near 
our  coast,  and  which  diffuses  the  warm  waters  of  the 
Caribbean  Sea  and  the  Gulf  of  Mexico  over  the 
Northern  Atlantic,  depositing  on  the  shores  of  Scot- 
land and  Norway  the  plants  and  seeds  of  the  tropics. 
It  is  solely  the  heat  which  these  waters  bring  with 
them  from  the  equator  that  has  made  the  island  of 
Great  Britain  so  great  a  centre  of  commerce  and  civ- 
ilization ;  for  it  must  be  remembered  that  the  latitude 
of  England  is  the  same  as  that  of  Labrador,  and, 
were  it  not  for  the  influence  of  this  ocean  current, 
her  soil  would  be  equally  desolate  and  barren.  If 
the  configuration  of  our  Western  Continent  were 
only  so  slightly  changed  as  to  give  a  passage  to  the 
equatorial  current  through  the  present  Isthmus  of 
Panama — a  change  insignificant  in  comparison  with 
those  which  have  heretofore  taken  place— "the 
mountains  of  Wales  and  Scotland  would  become 
again  the  abode  of  glaciers,  and  civilization  would 
disappear  before  the  invasion  of  arctic  cold."  ^  So 
also  it  is  to  the  enormous  mass  of  heated  water 
which  the  Gulf-Stream  pours  into  the  seas  surround- 


**W.  Hopkins's  Address  before  the  Geological  Society  of  Great 
Britain. 


POINT   OF   MAXIMUM   DENSITY.  I47 

inc^  northern  Europe  that  Sweden  and  Norway  owe 
their  temperate  climate,  while  at  the  corresponding 
latitudes  on  our  own  continent  the  land  is  shrouded 
in  eternal  ice  and  snow. 

But  all  these  provisions  for  distributing  heat 
over  the  earth's  surface  would  have  been  insuffi- 
cient to  maintain  organic  life  in  our  northern  cli- 
mate, were  it  not  for  still  another  remarkable 
property  with  which  water  has  been  endowed, — a 
property  even  more  entirely  unique  than  either  of 
those  we  have  studied,  and  one  which  seems  to  be 
an  exception  to  the  general  laws  of  nature.  The 
familiar  cycles  of  organic  life,  both  in  animals  and 
plants,  afe  intimately  associated  with  the  succession 
of  the  seasons,  and  this,  in  its  turn,  depends  on  the 
inclination  of  the  earth's  axis  to  the  plane  of  the 
ecliptic,  and  on  the  great  primary  laws  by  which 
this  axis  is  constantly  maintained  in  a  position  par- 
allel to  itself  during  the  revolution  of  the  planet 
around  the  sun.  To  these  fundamental  conditions 
in  the  formation  of  the  solar  system  the  whole  con- 
stitution of  organic  life  on  the  earth  has  been  ad- 
justed ;  and  Dr.  Whewell,  in  his  excellent  Bridge- 
water  Treatise,  has  discussed  at  length  the  evi- 
dences of  design  which  this  circumstance  affords. 
It  would  be  foreign  to  my  plan,  to  consider  these 
evidences  here;  but,  assuming  the  succession  of  the 
seasons  as  a  part  of  the  order  of  creation,  and  as  a 
means  of  adapting  a  larger  portion  of  the  earth's 
surface  to  the  habitation  of  organized  beings,  it  is 
evident  that  the  higher  forms  of  organic  life  could 
be  sustained  in  these  northern  regions  only  by  fur- 


148  POINT  OF  MAXIMUM   DENSITY. 

nishing  to  the  plants  and  animals  an  adequate  pro- 
tection against  the  intense  cold  of  winter,  and  thus 
preserving  the  growth  of  one  summer  until  the 
returning  sun  awakened  new  life  in  the  succeeding 
spring. 

The  required  protection  has  been  provided  by 
making  a  most  marked  exception  to  the  general 
laws  of  expansion  in  the  case  of  water.  It  is  the 
general  law  of  nature  that  all  substances  are  ex- 
panded by  heat  and  contracted  by  cold,  and  water 
forms  no  exception  to  the  general  rule,  except 
within  certain  very  narrow  limits  of  temperature, 
shortly  to  be  noticed.  Indeed,  were  it  not  for  the 
expansion,  we  could  not  readily  either  heat  or  cool 
a  large  mass  of  liquid  matter.  All  liquids  are  very 
poor  conductors  of  heat,  and  can  be  heated  only  by 
bringing  their  particles  successively  in  contact  with 
the  source  of  heat.  When  you  set  a  tea-kettle  over 
a  fire,  the  first  effect  of  the  heat  is  to  expand  the 
particles  of  water  resting  on  the  bottom  of  the 
kettle,  which,  being  thus  rendered  specifically  lighter, 
rise,  and  are  succeeded  by  colder  particles,  which 
are  heated  and  rise  in  their  turn ;  and  thus  the  cir- 
culation is  established  by  which  all  the  particles  are 
successively  brought  in  contact  with  the  heated  bot- 
tom of  the  kettle,  and  in  the  course  of  time  the 
temperature  of  the  whole  mass  is  raised  to  the 
boiling-point.  The  case  is  similar  when  you  add 
ice  to  a  pitcher  of  water  in  order  to  cool  it.  The 
water  at  the  top  of  the  pitcher,  in  contact  with  the 
ice  is,  of  course,  cooled,  and,  being  thus  rendered 
specifically   heavier   than    the   water    below,    sinks 


POINT  OF   MAXIMUM   DENSITY.  I49 

and  gives  place  to  the  warmer  water,  which  is 
cooled  and  sinks  in  its  turn,  and  thus,  as  before,  a 
circulation  is  established,  which  continues  until  the 
temperature  of  the  whole  water  is  reduced  to  40"^. 
But  at  this  point  the  circulation  is  entirely  arrested ; 
for,  in  consequence  of  its  singular  constitution, 
water  at  39°  is  lighter  than  water  at  40°,  and  con- 
sequently remains  at  the  top.  And  so  it  is  as  the 
temperature  sinks  toward  the  freezing-point.  The 
colder  the  water,  the  lighter  it  becomes,  and  the 
more  persistently  it  remains  at  the  surface.  Hence, 
although  the  upper  layers  of  water  may  be  readily 
cooled  to  the  freezing-point,  yet,  in  consequence  of 
its  poor  conducting  power,  the  great  body  of  the 
liquid  below  will  remain  at  the  temperature  of  40''. 
The  coTd^^atmosphere  of  winter  acts  upon  the 
ponds  and  lakes  exactly  as  the  ice  on  the  water  in 
the  pitcher.  They  also  are  cooled  from  the  surface, 
and  a  circulation  is  established  by  the  constant  sink- 
ing of  the  chilled  water  until  the  temperature  falls 
to  40°.  But  at  this  point,  still  eight  degrees  above 
the  freezing-point,  the  circulation  stops.  The  sur- 
face-water, as  it  cools  below  this  temperature,  re- 
mains at  the  top,  and  in  the  end  freezes ;  but  then 
comes  into  play  still  another  provision  in  the  proper- 
ties of  water.  Most  substances  are  heavier  in  their 
solid  than  in  their  liquid  state ;  but  ice,  on  the  con- 
trary, is  lighter  than  water,  and  therefore  floats  on 
its  surface.  Moreover,  as  ice  is  a  very  poor  conduc- 
tor of  heat,  it  serves  as  a  protection  to  the  lake,  so 
that  at  the  depth  of  a  few  feet,  at  most,  the  tem- 
perature of  the  water  during  winter  is  never  under 


I50  ICE   LIGHTER  THAN  WATER. 

40°,   although   the  atmosphere   may   continue    for 
weeks  below  zero. 

If  water  resembled  other  liquids,  and  continued  to 
contract  with  cold  to  its  freezing-point, — if  this  ex- 
ception had  not  been  made,  the  whole  order  of 
nature  would  have  been  reversed.  The  circulation 
just  described  would  continue  until  the  whole  mass 
of  water  in  the  lake  had  fallen  to  the  freezing-point. 
The  ice  would  then  first  form  at  the  bottom,  and  the 
congelation  would  continue  until  the  whole  lake  had 
been  changed  into  one  mass  of  solid  ice.  Upon 
such  a  mass  the  hottest  summer  would  produce  but 
little  effect ;  for  the  poor  conducting  power  would 
then  prevent  its  melting,  and  instead  of  ponds  and 
lakes  we  should  have  large  masses  of  ice,  which 
during  the  summer  would  melt  on  the  surface  to  the 
depth  of  only  a  few  feet.  It  is  unnecessary  to  state 
that  this  condition  of  things  would  be  utterly  incon- 
sistent with  the  existence  of  aquatic  plants  or  an- 
imals, and  it  would  be  almost  as  fatal  to  organic  life 
everywhere  ;  for  not  only  are  all  parts  of  the  creation 
so  indissolubly  bound  together  that,  if  one  member 
suffers,  all  the  other  members  suffer  with  it,  but 
moreover,  the  soil  itself  would,  to  a  certain  extent, 
share  in  the  fate  of  the  ponds.  The  soil  is  always 
more  or  less  saturated  with  water,  and,  under  exist- 
ing conditions  in  our  temperate  zone,  the  frost  does 
not  penetrate  to  a  sufHcient  depth  to  kill  the  roots 
and  seeds  of  plants  which  are  buried  under  it.  But 
were  water  constituted  like  other  liquids,  the  soil 
would  remain  frozen  to  the  depth  of  many  feet,  and 
the  only  effect  of  the  summer's  heat  would  be  to 


THE   FROST  BLANKET.  15I 

melt  a  few  inches  at  the  surface.  It  would  be,  per- 
haps, possible  to  cultivate  some  hardy  annuals  in 
such  a  climate,  but  this  would  be  all.  Trees  and 
shrubs  could  not  brave  the  severity  of  the  winter. 
Thus,  then,  it  appears  that  the  very  existence  of  life 
in  these  temperate  regions  of  the  earth  depends  on 
an  apparent  exception  to  a  general  law  of  nature,  so 
slight  and  limited  in  its  extent  that  it  can  only  be 
detected  by  the  most  refined  scientific  observation. 

Moreover,  this  exceptional  property  is  united  in 
water  with  another  quality,  which  greatly  aids  in 
preserving  vegetable  life  during  the  winter  months. 
We  shudder  at  the  thought  of  snow,  but  neverthe- 
less it  affords  a  most  effectual  protection  to  the  soil, 
forming  as  warm  a  covering  as  would  the  softest 
wool.  Water  in  all  its  conditions  has  been  made  a 
very  bad  conductor  of  heat,  and  snow  is  ranked  with 
wool  among  the  poorest  of  conductors.  Heat,  there- 
fore, cannot  readily  escape  from  a  snow-covered  so]], 
and  thus  its  temperature  is  prevented  from  falling 
materially  below  the  freezing-point,  however  great 
the  severity  of  the  season.  Notice  now,  that,  when 
winter  sets  in  and  the  cold  increases  to  such  a  degree 
as  to  endanger  the  tender  plants.  Nature  promptly 
spreads  her  great  frost -blanket  over  forest,  prai- 
rie, meadow,  and  garden  alike,  so  that  all  may  slum- 
ber on  in  safety  until  the  sun  returns  and  melts  away 
the  downy  covering,  when  the  buds  break  forth 
again  and  the  trees  put  on  a  new  mantle  of  living 
green. 

This  leads  me  to  speak  of  still  another  remarkable 
property  of  the  wonderful  liquid  we  are  studying  ; 


152  HEAT  OF  FUSION. 

for  nature  has  provided  in  the  constitution  of  water 
a  most  effectual  means  of  tempering  the  transition 
of  the  seasons,  and  protecting  vegetation  against 
the  early  frosts  of  autumn  or  the  first  deceptive 
glow  of  returning  spring.  In  order  to  freeze  a  liquid 
it  is  necessary  to  remove  from  it  a  certain  quantity 
of  heat  called  the  heat  of  fusion,  and  the  more  of 
this  heat  a  liquid  contains,  with  the  more  difficulty, 
of  course,  it  freezes,  and  when  once  frozen  the  less 
readily  the  solid  melts.  Now  water  contains  a 
larger  amount  of  heat  of  fusion  than  any  other 
liquid  yet  examined,  and  in  this  respect,  therefore, 
it  is  also  peculiarly  constituted.  And  mark  how  this 
property  tends  to  produce  the  result  just  noticed. 
As  the  weather  becomes  cooler  in  autumn,  our  ponds 
and  lakes  gradually  give  up  the  stores  of  heat  which 
they  contain,  until  the  temperature  of  the  whole 
mass  of  water  is  reduced  to  40°  ;  then  the  surface- 
water  cools  still  further  to  the  freezing-point ;  but 
before  it  can  beconle  any  colder  than  this  the  water 
must  freeze,  and  in  freezing  it  will  set  free  four 
times  as  much  heat  as  it  has  already  given  out  in 
cooling  from  the  temperature  of  summer  (63°)  to  the 
freezing-point.  It  is  evident,  therefore,  that  freez- 
ing must  be  a  slow  process.  Moreover,  it  is  also  a 
warming  process,  and  although  the  temperature  of 
surrounding  objects  can  never  be  thus  raised  above 
the  freezing-point,  nevertheless  the  immense  amount 
of  heat  evolved  greatly  tends  to  retard  the  approach 
of  severe  cold,  and  prepares  the  way  for  the  inclem- 
ency of  winter.  So  also,  when  spring  comes,  vege- 
tation  is  not    awakened  by  her  first  touch  to  be 


HEAT   OF  FUSION.  I53 

exposed  to  the  blights  of  the  early  frosts,  and  before 
the  snow  covering  can  be  melted  off  the  danger  is 
mostly  passed.  Again,  when  we  consider  what  de- 
vastating floods  would  sweep  the  earth  were  the  icy 
bonds  of  winter  suddenly  dissolved,  we  shall  dis- 
cover still  further  evidence  of  the  wisdom  of  that 
Being  who  has  so  adjusted  the  properties  of  water 
that  both  frost  and  freshet  are  the  exception,  not 
the  rule. 

I  have  said  that  water  presents  the  only  well- 
established  exception  to  the  laws  of  expansion  by 
heat,  and  some  writers  on  natural  theology  have 
dwelt  on  this  point  as  one  of  great  importance  to 
their  argument.  But  I  cannot  think  they  are  wise ; 
for,  to  say  the  least,  they  rest  their  argument  on  our 
ignorance,  and  not  on  our  knowledge.  It  is  true 
that  in  the  present  state  of  science  the  anomalous 
expansion  of  water  near  the  freezing-point  seems  to 
be  an  exception'^  to  the  general  laws  of  nature;  but 
hereafter  this  very  anomaly  may  appear  to  be  the 
natural  result  of  a  more  general  law  not  yet  dis- 
covered, or,  like  the  perturbations  in  the  orbits  of 
the  planets,  may  prove  to  be  the  strongest  confirma- 
tion of  the  very  law  it  now  seems  to  invalidate. 
Moreover,  I  do  not  share  in  that  indefinite  dread  of 
natural  laws  which  troubles  so  many  religious  minds. 
To  me  the  laws  of  nature  afford  the  strongest  evi- 
dences of  the  existence  of  a  God,  and  in  their  uni- 
formity I  see  merely  the  constant  action  of  an  omni- 
present   Creator,  who    acts  with   perfect  regularity 

*  The  peculiarity  consists  in  the  anomalous  expansion  of  water,  not 
in  the  fact  that  water  expands  in  freezing,  as  stated  by  some  w^riters, 

7* 


154  NATURE   OF  THE  EVIDENCE. 

because  he  acts  consistently  and  with  infinite  wis- 
dom. I  beHeve  that  all  parts  of  nature  are  correlated 
by  laws,  and  that  the  wider  our  knowledge  becomes, 
the  more  universal  these  laws  will  appear.  I  do  not, 
therefore,  regard  the  constitution  of  water  as  some- 
thing apart  from  law,  and  as  the  evidence  of  a  power 
coming  down,  as  it  were,  upon  law  to  make  an  ex- 
ception to  it.  This  is  making  altogether  too  much 
of  law.  God  is  not  bound  by  law.  He  acts  wisely, 
beneficentry,  and  with  a  definite  plan,  and  the  most 
we  can  claim  for  natural  laws  is,  that  they  are  our 
imperfect  human  expressions  of  this  Divine  plan. 
Moreover,  that  is  a  far  nobler  view  of  God's  wisdom 
which  supposes  Him  to  be  able  to  harmonize  special 
adaptations  with  general  laws.  What  I  find  so  re- 
markable in  the  constitution  of  water  is,  not  that  it 
is  an  exception  to  the  general  laws  of  nature,  but 
that,  while  filling  its  place  in  the  general  plan,  it 
has  been  endowed  with  such  extreme  properties, 
and  that  in  each  case  the  peculiar  property  has 
special  adaptations  at  once  so  complex  and  so  impor- 
tant. Not  only  has  water  this  exceptional  property 
of  expanding  when  other  liquids  contract,  but,  more- 
over, of  all  known  substances  it  has  the  greatest 
capacity  for  heat ;  so  also,  when  changing  into  va- 
por, it  absorbs  more  heat  than  any  other  liquid  ; 
again,  it  is  far  lighter  in  the  solid  than  in  the  liquid 
state  ;  and  lastly,  it  contains  the  largest  amount  of 
heat  of  fusion  as  yet  observed  in  any  substance. 
All  this  may  be  in  harmony  with  general  laws.  I 
have  no  doubt  that  it  is ;  but  the  existence  of  the 
law  does  not  in  the  least  impair  the  significance  of 


NATURE   OF   THE   EVIDENCE.  155 

the  fact,  that  in  each  of  these  respects  water  has 
been  pecuHarly  constituted.  This  one  liquid  of  the 
globe,  which  covers  more  than  three-fourths  of  its 
surface,  which  circulates  through  all  its  channels, 
which  percolates  through  all  its  pores,  which  consti- 
tutes three-fourths  of  all  organized  beings,  has  been 
endowed  with  these  four  pre-eminent  qualities,  on 
each  of  which  the  whole  order  of  terrestrial  nature 
may  be  said  to  depend.  I  cannot  conceive  of  stronger 
evidence  of  design  than  this  ;  and  if  these  facts  do 
not  prove  the  existence  of  an  intelligent  Creator, 
then  all  nature  is  a  deception  and  our  own  faculties 
a  lie.  Yet,  my  friends,  this  is  only  a  small  part  of 
the  evidence  of  design  which  science  has  discovered 
in  this  familiar  liquid.  I  might  occupy  several  lec- 
tures with  this  subject  alone,  but  I  have  time  only 
to  glance  at  two  more  striking  facts. 

Water  is  the  most  universal  solvent  known,  and 
there  are  but  few  substances  which  are  not,  to  a 
greater  or  less  degree,  dissolved  by  it.  Those  which 
we  call  insoluble  generally  differ  from  the  rest  only 
in  degree.  Thus,  all  lime  rocks  dissolve  to  a  limited 
extent  in  spring  water,  and  the  same  is  also  true 
of  almost  all  mineral  substances.  The  magnificent 
crystals  which  we  frequently  find  in  the  rocks  are 
formed  in  almost  every  case  by  a  deposition  of  the 
mineral  substance  from  a  state  of  solution  in  water. 
The  feeble  solvent  power  of  the  water  for  these  sub- 
stances is  made  up  by  the  large  volume  of  the 
solution,  and  the  length  of  time  occupied  in  the 
process  of  crystallization.  Many  of  the  large  crys- 
tals which  may  be  seen  in  cabinets  of  minerals  have 


156  SOLVENT   POWER. 


been  unquestionably  thousands  of  years  in  formation. 
And  not  only  does  the  solvent  power  of  water  stud 
the  cavities  of  the  rocks  with  gems,  but  it  is  also 
constantly  producing  most  important  changes  in 
the  rocky  structures  of  the  globe  itself,  here  cement- 
ing together  the  loose  sands,  and  there  converting 
the  soft  clays  into  firm  and  solid  rock. 

Again,  the  solvent  power  of  water  extends  to 
aeriform  as  well  as  to  the  solid  substances,  so  that 
the  gases  composing  the  air  pervade  the  lakes  and 
the  oceans  as  well  as  the  atmosphere.  Indeed,  it  is 
on  the  gases  dissolved  in  the  water  that  all  the  aqua- 
tic plants  and  animals  live,  and  the  members  of  the 
various  finny  tribes  breathe  the  free  oxygen  dis- 
solv^ed  in  the  water,  as  we  breathe  the  oxygen  of 
the  air.  Again,  the  process  of  respiration  is  essen- 
tially the  same  with  these  lower  animals  that  it  is 
with  us,  and  the  structure  of  their  organs  has  been 
adjusted  to  the  amount  of  this  life-sustaining  ele- 
ment which  water  is  capable  of  dissolving.  More- 
over, the  power  which  water  possesses  of  dissolving 
oxygen  is  much  greater  than  its  power  of  dissolving 
nitrogen,  and  hence  the  air  dissolved  in  the  ocean 
is  proportionally  much  richer  in  oxygen  than  our 
atmosphere.  This  is  undoubtedly  another  quality 
with  which  water  has  been  endowed  in  order  to 
render  the  oceans,  the  lakes,  and  the  rivers  a  fit 
habitation  for  that  world  of  organic  life  which  mod- 
ern zoology  has  revealed.  That  we  are  unable  to 
trace  all  its  relations,  is  evidently  owing  to  the  im- 
perfection of  our  knowledge.  But  here  a  new  field 
of  study  opens  before  us,  which,  when  fully  explored, 


CHEMICAL  RELATIONS.  157 

will  undoubtedly  prove  as  rich  in  the  evidence  of 
design  as  the  atmosphere  itself. 

It  is  not,  however,  merely  as  a  solvent,  that  water 
is  an  important  agent  in  the  great  laboratory  of  the 
world.  I  have  already  stated  to  what  extent  all 
animal  and  vegetable  substances  are  composed  of 
water,  and  that  some,  such  as  the  jelly-fishes  among 
animals,  and  the  gourd  family  among  plants,  may  be 
said  to  be  living  forms  of  water.  But  we  should 
entertain  a  very  erroneous  conception  of  the  condi- 
tion of  the  water  in  these  animal  and  vegetable 
structures,  were  we  to  regard  it  as  so  much  dead 
material,  building  up  the  form  like  the  bricks  in  an 
edifice.  This  water  is  in  constant  circulation,  con- 
veying nourishment  to  all  the  parts,  and  at  the  same 
time  removing  from  the  system  those  tissues  which 
have  fulfilled  their  functions  and  become  effete.  It 
is  being  constantly  decomposed,  and  as  rapidly  again 
reformed,  assuming  the  most  protean  conditions, 
and  administering  to  the  functions  of  the  animal 
economy  in  a  thousand  ways. 

As  a  constituent  of  inorganic  matter,  water  is  no 
less  important  than  it  is  in  organized  being.  A  sub- 
stance so  bland  as  water,  and  apparently  so  entirely 
inactive,  which  fills  the  most  delicate  vegetable 
cells,  and  penetrates  the  finest  capillaries  of  the 
body, — whose  minuteness  and  delicacy  no  art  can 
approach,  nor  imagination  scarcely  conceive, — yet 
without  affecting  either  in  the  slightest  degree,  we 
should  suppose  would  be  endowed  with  no  affini- 
ties, and  capable  of  exerting  no  chemical  force. 
Yet  what  is  the  fact?     In  attempting   to   classify 


IS8  COMPOSITION   OF  WATER. 

chemical  compounds,  I  have  studied  with  care  the 
chemical  history  of  water,  and  its  relations  to  other 
substances,  and  it  is  still  to  me  a  perfect  enigma  in 
nature.  For,  so  far  from  being  that  inert  material 
which  its  bland  exterior  would  seem  to  indicate,  it 
is  among  the  most  important  of  chemical  agents, 
forming  some  of  the  most  stable  compounds,  and 
surprising  the  chemist  by  the  strength  of  its  affini- 
ties. Not  only  is  water  a  common  constituent  of 
most  crystalline  salts,  and  an  essential  ingredient  of 
many  of  the  powerful  acids  which  are  used  both 
in  the  arts  and  in  the  chemist's  laboratory,  but  it 
makes,  also,  a  not  unimportant  part  of  the  rocky 
crust  of  the  globe.  Besides  forming  the  immense 
deposits  of  ice  which  perpetually  surround  either 
pole,  and  the  glaciers  which  creep  down  the  high 
mountain  slopes,  we  find  that  water  enters  as  an 
essential  ingredient  into  the  composition  of  talcose 
and  chlorite  slate,  gypsum,  serpentine,  soapstone, 
and  other  rocks.  Moreover,  water  is  the  medium 
in  which  most  chemical  processes  take  place,  and 
throughout  all  geological  history  it  has  been  pro- 
ducing the  most  fundamental  changes  in  the  com- 
position of  the  earth's  crust,  the  extent  of  which 
geologists  are  only  of  late  beginning  to  appreciate. 
It  is  now  supposed  that  granite  and  similar  rocks, 
which  were  formerly  regarded  as  products  of  igne- 
ous fusion,  have  been  really  formed  from  loose 
beds  of  mud  and  clay,  through  the  transforming 
power  of  this  wonderful  and  powerful  agent. 

When,  lastly,  we    consider    the    composition    of 
water,  our  wonder  is  still  further  increased ;  for  it 


LATENT   POWER.  1 59 


consists  of  two  permanent  gases,  condensed  by  the 
force  of  chemical  affinity  to  the  liquid  condition. 
With  one  of  these,  oxygen,  you  are  already  famil- 
iar. The  other  is  a  light,  combustible  gas,  called 
hydrogen,  fourteen  and  a  half  times  lighter  than 
air,  and  by  far  the  lightest  form  of  matter  known. 
One  cubic  foot  of  water  yields  more  than  eighteen 
hundred  cubic  feet  of  a  mixture  of  these  two  gases, 
and  so  persistently  do  they  retain  their  aeriform 
condition,  that  not  even  a  pressure  of  twenty  tons 
on  the  square  inch  is  sufficient  to  reduce  them 
to  liquids.  Yet,  immense  as  this  pressure  seems, 
requiring  all  the  mechanical  skill  of  man  to  apply  it, 
that  force  must  be  still  greater  which  is  constantly 
acting  in  every  drop  of  water  to  hold  these  highly 
elastic  gases  in  the  liquid  state.  It  is  difficult  to 
estimate  the  magnitude  of  such  power,  as  our  only 
standard  of  measurement  is  the  quantity  of  some 
other  force,  equally  immeasurable,  which  is  required 
to  balance  the  first.  Water  is  easily  decomposed 
by  electricity,  and  the  amount  of  this  agent  required 
to  force  apart  its  constituents  may  perhaps  give  you 
some  imperfect  conception  of  the  magnitude  of 
that  power  by  which  they  are  so  securely  impris- 
oned. The  statement  may  seem  incredible,  but  yet 
it  has  been  proved  by  Professor  Faraday,  that  it 
requires  more  electricity  to  decompose  a  drop  of 
water  than  to  charge  a  thunder-cloud. 

What  a  revelation  of  power  we  have  here  !  In 
every  drop  of  water  there  is  a  constant  striving  of 
the  elements  to  escape;  they  are  exerting  a  force 
to  break  the  bonds  that  unite  them,  which  can  be 


l6o  SUMMING    UP 


measured  only  by  the  power  of  concentrated  thun- 
der-bolts, and  yet  this  immense  force  is  kept  in 
check  by  a  force  of  equal  power,  and  so  exactly  bal- 
anced that  not  the  slightest  disturbance  can  occur. 
When  now  I  endeavor  to  estimate  the  value  of  this 
chemical  force  by  our  human  standards,  and  find 
that  in  comparison  with  it  all  the  mechanical  en- 
ergy which  man  can  exert,  even  when  aided  by  the 
appliances  of  modern  art,  is  utterly  insignificant ; 
and  when  I  reflect  that  in  every  particle  of  water 
the  force  is  still  acting,  so  that  every  rain-drop 
which  falls  is  a  silent  monitor  of  human  weakness, 
I  am  overwhelmed  by  that  mystery  in  nature,  which, 
here  as  elsewhere,  ever  points  upward  to  the  Infinite, 
and  thus  silently  teaches  that  the  mighty  influence 
which  binds  the  atoms  of  the  rain-drop  is  merely 
the  manifestation  of  His  ceaseless  power  who  hold- 
eth  ''  the  waters  in  the  hollow  of  His  hand." 
f  It  is  a  very  common  mistake  to  suppose  that 
/the  grand  in  nature  is  to  be  seen  only  in  its 
i  great  water-falls  and  its  lofty  mountains  ;  for,  to 
the  intellectual  eye,  there  is  more  real  grandeur, 
more  evidence  of  omnipotence,  in  a  single  rain- 
drop than  in  the  rush  of  Niagara  or  in  the  magni- 
tude of  Mont  Blanc.  The  more  I  study  the  evi- 
dence of  design  in  this  simple  liquid,  the  more  I 
find  there  is  to  learn,  and  I  feel  the  utter  inade- 
quacy of  any  language  to  convey  the  full  and  com- 
plete idea.  Review,  for  a  moment,  the  examples 
of  adaptation  which  have  been  so  briefly  noticed. 
Remember  that  water  is  the  liquid  of  our  globe, 
and  the  only  liquid  which  exists  in  any  abundance 


SUMMING   UP.  l6l 


on  its  surface.  The  total  amount  of  all  other  liquids 
is  in  comparison  but  as  *'  a  drop  of  a  bucket."  Con- 
sider, next,  that  its  specific  gravity  has  been  so  ad- 
justed that  our  ships  float,  and  the  oceans  are  made 
great  highways  for  the  nations ;  that  it  is  easily  con- 
verted into  vapor,  and  as  easily  condensed  to  fer- 
tilizing rain  and  refreshing  dew,  which  nourish  the 
growing  plants,  fill  the  springs,  and  keep  the  rivers — 
the  great  arteries  of  the  globe — in  circulation ;  that 
at  a  comparatively  low  temperature  it  is  changed 
into  highly  elastic  steam,  which,  imprisoned  by  man 
in  his  iron  boilers,  has  become  the  great  civilizer  of 
the  world  ;  that  it  has  been  so  exceptionally  consti- 
tuted that  the  great  mass  cannot  be  cooled  below 
forty  degrees,  and  again  has  been  made  such  a  poor 
conductor  of  heat  that,  when  the  surface  is  frozen,  the 
very  ice  becomes  a  protection  against  the  cold  ;  that 
to  this  same  liquid  there  has  been  given  a  very  great 
capacity  for  heat,  and  that  thus  it  has  been  made 
the  means  of  tempering  materially  the  climates  of 
the  globe.  Add  to  this  that  water  has  been  made 
an  almost  universal  solvent ;  that  from  the  sub- 
stances it  holds  in  solution  the  Crustacea  form  their 
shells  and  the  coral  polyps  build  their  reefs  ;  that  it 
fills  the  cavities  of  the  rocks  with  gems,  and  their  fis- 
sures with  useful  ores.  In  connection  with  this  host 
of  wonderful  mechanical  adaptations,  remember  that 
water  has  been  made  a  chemical  agent  of  great 
energy  and  power ;  that  there  have  been  united  in 
it  the  apparently  incompatible  qualities  of  bland- 
ness  and  great  chemical  force ;  that,  although  in  the 
laboratory  of  nature  it  corrodes  the  most  resisting 


l62  SUMMING   UP. 


rocks,  it  also  circulates  through  the  leaflets  of  the 
rose  and  the  still  more  delicate  human  lungs ;  that 
it  forms  the  greater  part  of  all  organized  beings, 
from  the  lichen  to  the  oak,  and  from  the  polyp  to 
man.  Reflect,  now,  that  these  are  only  a  few  of  the 
grosser  qualities  and  functions  of  this  remarkable 
compound,  gleaned  here  and  there  from  many 
others  no  less  wonderful,  and  you  will  form  still 
but  a  very  imperfect  conception  of  the  amount  of 
design  which  has  been  crowded  into  it.  Attempt 
to  find  a  liquid,  which,  if  in  sufficient  quantity, 
might  supply  its  place,  and  you  will  be  still  further 
impressed  by  this  evidence  of  intelligence  and  fore- 
thought. Of  all  the  materials  of  our  globe,  water 
bears  most  conspicuously  the  stamp  of  the  Great 
Designer,  and  as  in  the  Book  of  Nature  it  teaches 
the  most  impressive  lesson  of  His  wisdom  and 
power,  so  in  the  Book  of  Grace  it  has  been  made  a 
token  of  God's  eternal  covenant  with  man,  and  still 
reflects  His  never-fading  promise  from  the  painted 
bow. 


CHAPTER    VI. 

TESTIMONY   OF   CARBONIC   DIOXIDE. 

When  standing  by  some  quiet  mill-stream,  have 
you  ever  speculated  on  the  origin  of  the  power  which 
is  animating  the  machinery  of  the  great  factory  on 
its  banks,  spinning  and  weaving  the  crude  cotton 
into  miles  of  cloth  every  week?  Or  at  Niagara,  did 
the  thought  ever  strike  you,  when  gazing  up  at 
those  floods  of  water  which  come  tumbling  over 
the  rocky  cliffs,  and  plunging  into  the  seething  sea 
at  your  feet,  that  similar  floods  had  been  pouring 
over  that  ancient  river-bed  for  countless  ages  with- 
out diminishing  the  inexhaustible  supply?  Or,  if 
it  has  been  at  once  your  privilege  and  your  terror 
to  witness  that  grandest  sight  of  nature,  a  violent 
storm  at  sea,  have  you  been  impressed  by  the  un- 
tiring might  of  that  mysterious  agent  which  impels 
the  raging  winds  and  upheaves  the  roaring  billows? 
Whence  can  come  all  the  power?  and  what  keeps 
in  motion  that  wonderful  aqueous  circulation,  which 
we  studied  in  the  last  chapter? 

Although  the  origin  of  this  never-ceasing  motion 
may  be  still  concealed,  we  have  at  least  traced  back 

163 


164  CIRCULATION  OF  CARBON. 

the  power  to  a  proximate  source  in  the  great  central 
luminary  of  our  system.  It  is  the  gentle  influences 
of  the  sunbeam  that  raise  the  water  in  vapor,  and 
it  is  the  same  solar  rays  that  keep  in  motion  the 
great  aerial  currents,  spreading  the  clouds  over 
the  earth,  and  distilling  their  liquid  treasures  "  to 
satisfy  the  desolate  and  waste  ground,  and  to  cause 
the  bud  of  the  tender  herb  to  spring  forth."  In- 
credible as  it  may  appear,  it  is  actually  the  sun 
that  weaves  the  cloth,  that  feeds  the  fountains  of 
Niagara,  and  it  is  his  delicate  rays  that  rule  in 
the  tempest  and  direct  the  storm.  But  there  are 
other  influences  of  the  sunbeam  still  more  subtle 
than  these,  and  there  are  other  cycles  of  changes,  as 
grand  as  the  aqueous  circulation,  of  which  the  sun 
is  also  the  ever-active  cause. 

Referring  to  the  table  before  given,  representing 
the  composition  of  the  atmosphere,  you  will  notice 
that  the  great  aerial  ocean  contains  more  than  five 
million  billions  of  tons  of  an  aeriform  substance 
called  carbonic  dioxide.  This  amount,  although 
absolutely  very  great,  is  nevertheless  only  a  small 
fraction  of  the  whole  atmosphere,  making  up  less 
than  a  thousandth  part  of  its  total  mass.  A  cubic 
foot  of  air  does  not  contain  more  than  a  quarter 
of  a  grain  of  carbonic  dioxide  ;  yet  there  is  not 
one  of  the  atmospheric  constituents  more  intimately 
associated  with  organic  life,  or  which  discharges 
more  important  functions.  Although  itself  a  col- 
orless gas,  carbonic  dioxide  consists  of  ordinary 
black  charcoal  combined  with  oxygen,  and  these 
elements  are  united  by  one  of  the  strongest  affini- 


CIRCULATION   OF   CARBON.  165 

ties  known  in  nature ;  yet,  intense  as  this  force  is, 
the  power  of  the  sun  is  greater,  and  his  rays,  acting 
on  the  green  leaves  of  the  plants,  are  constantly 
decomposing  the  gas  and  Hberating  the  carbon,  to 
be  incorporated  into  the  various  forms  of  vegetable 
life.  Here,  however,  it  remains  only  for  a  brief 
period ;  for  when  the  plants  have  finished  their 
allotted  term  of  life,  the  carbon  again  unites  with 
oxygen,  and,  in  the  form  of  carbonic  dioxide,  is 
restored  to  the  atmosphere  by  the  process  of  com- 
bustion or  decay.  But  frequently,  before  these 
destructive  changes  complete  the  cycle,  the  car- 
bon undergoes  a  further  transformation,  and  through 
the  process  of  digestion  becomes  a  part  of  the  body 
of  the  animal.  Yet  this  transmutation,  as  a  general 
rule,  only  hastens  the  final  result ;  since  the  processes 
of  animal  life  are  very  rapid,  and  sooner  or  later  the 
carbon  is  burnt  up  in  the  body,  and  breathed  out 
into  the  atmosphere,  ready  to  renew  the  same  series 
of  changes.  In  this  lecture  I  wish  to  ask  your  atten- 
tion to  the  evidences  of  design  which  may  be  dis- 
covered by  studying  this  wonderful  circulation  of 
carbon ;  and  we  shall  find  that  the  properties  both 
of  carbon  and  carbonic  dioxide  have  been  most 
carefully  adjusted  to  the  part  which  they  play  in 
the  great  scheme  of  nature.  We  might  begin  our 
study  at  any  link  of  this  endless  chain  of  phenom- 
ena; but  to  bring  the  subject  into  orderly  con- 
nection with  our  previous  trains  of  thought,  let  us 
return  to  the  phenomena  of  combustion,  which  we 
considered  in  the  third  chapter,  and  study  the  de- 
tails of  this  familiar  process  a  little  more  closely. 


l66  COMPOSITION  OF  FUEL. 

All  fuel,  without  exception,  contains  charcoal,  or, 
as  the  chemists  call  it,  carbon.  Wood,  soft  coal, 
oil,  wax,  similar  combustibles,  which  burn  with 
flame,  contain,  besides  carbon,  a  variable  quantity 
of  hydrogen  and  oxygen  ;  but  hard  coal,  coke,  and 
common  wood  charcoal  are  almost  pure  carbon. 
The  adaptations  of  each  of  these  classes  of  combus- 
tibles demand  special  notice,  and  let  us  begin  by 
studying  the  evidences  of  design  which  are  to  be 
found  in  an  ordinary  hard-coal  fire ;  and  while,  in 
imagination,  we  are  preparing  the  fire  to  be  lighted 
on  the  grate,  we  may  study  with  profit  some  of  the 
external  properties  of  the  coal,  for  even  they  betray 
the  master-hand  of  the  Great  Architect. 

Examining  closely  this  lump  of  charcoal,  you  will 
notice  that  it  retains  all  the  delicate  structure  of 
the  wood  from  which  it  was  prepared.  Here  is  the 
fibrous  bark  next  the  sap-wood,  and  then  the  annual 
rings,  all  as  on  a  stick  of  beech  ;  and  if  you  will 
take  the  pains  to  make  a  thin  section  of  the  char- 
coal, you  will  find,  on  examining  it  with  a  mi- 
croscope, that  the  minutest  cells  have  been  pre- 
served. You  know  how  charcoal  is  made.  The 
wood  is  exposed  to  a  high  temperature  in  the  char- 
coal mounds  or  furnaces,  by  which  the  gases  which  it 
contains  are  driven  off,  while  the  charcoal,  not  being 
volatile,  remains  behind.  Here,  then,  is  a  remark- 
able fact, — that,  although  the  wood  has  been  ex- 
posed to  a  red  heat  in  the  process  of  carbonization, 
yet  the  minutest  cells  have  not  been  destroyed;  and 
it  illustrates  an  equally  remarkable  quality  of  char- 
coal, on  which,  as  we  shall  see,  its  usefulness  as  fuel 


INFUSIBILITY   OF   CARBON.  167 

very  greatly  depends.  Carbon,  in  all  its  forms,  is 
absolutely  infusible.  It  does  not  even  soften  at  the 
highest  temperatures  which  can  be  attained  by  art, 

-^nd  it  is  for  this  reason  that  the  charcoal  retains  so 
perfectly  the  structure  of  the  wood.  Were  carbon 
fusible  at  a  red  heat,  the  charcoal  would  run  together 
into  a  shapeless  mass  in  the  mounds  or  furnaces 
in  which  it  is  prepared,  and  did  it  even  soften  at  this 
temperature,  the  forms  of  these  delicate  cells  could 
never  have  been  preserved.  Viewed  in  connection 
with  the  volatile  qualities  of  the  other  elements  of 
organized  beings,  the  extreme  fixity  of  carbon  in  its 
uncombined  condition  is  worthy  of  your  special 
attention.  The  only  other  essential  elements  of 
organic  matter  are  oxygen,  hydrogen,  and  nitrogen ; 
and  these  three  substances  are  not  only  gases,  but 
gases  which,  even  at  the  lowest  natural  temperature 
cannot  be  condensed  to  the  liquid  condition  by  press- 
ure alone  ;  yet  so  strong  is  the  tendency  of  carbon 
to  remain  solid,  that  it  condenses  these  gases  around 
itself  in  every  organized  substance  that  exists.  Car- 
bon is  thus  the  solid  substratum  of  organized  mat- 
ter, the/  skeleton,  as  it  were,  of  every  organic  form. 
How  evidently,  then,  has  the  attribute  of  infusibility 
been  adapted  to  this  important  function  which  car- 
bon has  been  appointed  to  subserve  ! 

Examining  again  this  lump  of  charcoal  which  we 
are  using  to  kindle  the  fire,  mark  that  it  has  a 
black  color  and  is  perfectly  opaque.  These  qualities 
are  so  evident  to  the  most  superficial  observation 

^that  they  are  apt  to  pass  unnoticed,  and  yet  it  is 
these  qualities  of  charcoal  which  make  it  so  valu- 


1 68  BLACK  COLOR  AND   OPACITY. 

able  as  a  basis  of  printing  ink.  All  may  not 
know  that  printing  ink  is  a  mixture  of  lamp-black 
and  oil,  and  that  the  letters  on  a  printed  page 
are  formed  by  thin  layers  of  black  charcoal  spread 
over  the  white  paper;  and  charcoal  is  peculiarly 
well  adapted  for  this  use,  since,  however  finely  sub- 
divided, it  never  loses  its  dead  black  color  and  per- 
fect opacity.  But  this  property  of  charcoal  would 
be  useless  to  the  scholar  for  diffusing  knowledge, 
were  it  not  combined  with  qualities  still  more  re- 
markable, and  almost  unique.  Carbon  is  not  acted 
upon  by  atmospheric  agents,  and,  moreover,  is  abso- 
lutely insoluble  in  any  liquid,  with  the  exception 
of  melted  iron.  The  letters  of  the  first  Bible  ever 
printed  are  as  black  as  they  were  the  day  they  left 
the  types.  They  have  been  exposed  to  the  action  of 
atmospheric  air  for  four  hundred  years,  and,  were 
carbon  in  the  slightest  degree  acted  upon  by  the 
atmosphere,  they  would  long  since  have  disap- 
peared. As  it  is,  they  will  endure  as  long  as  the 
paper  on  which  they  are  printed  lasts. 

The  almost  unparalleled  insolubility  of  charcoal  is 
a  quality  equally  important  in  this  relation,  for,  were 
charcoal,  even  to  a  slight  extent,  soluble  in  water, 
the  books  of  our  fathers  would  have  been  rendered 
illegible  by  the  dainpness  to  which  all  libraries  are 
more  or  less  exposed ;  and  were  carbon  soluble  even 
in  such  liquids  as  alcohol,  ether,  or  the  volatile  oils, 
the  printed  page  would  not  have  been,  as  now,  safe 
from  alteration,  and  all  kinds  of  fraud  would  have 
been  easy.  We  justly  honor  the  names  of  Guten- 
berg and  Faust,  whose  art  has  done  so  much  to  en- 


PERMANENCY. 


lighten  and  civilize  the  globe,  and  we'bestoi^due    i* 
admiration   on   those   improvements  in  the  aro  qL        O  >^ 
printing,  nowhere  more  developed  than  in  our  owry'^.  / 
land,  which   have  made  the  press  the  great  agent      *     // 
of  power,  and  elevated  the  moral  and  intellectual 
above  the  physical  man  ;  but  while  we  pay  just  trib- 
ute to  the  genius  of  these  benefactors  of  the  race, 
let  us  not  forget  that  greater  Benefactor,  who  was 
before  them  all;  for  in  the  most  familiar  qualities 
of  this  piece  of  charcoal,  on  which  the  art  of  print- 
ing so  greatly  depends,  there  has  been  displayed, 
since  the  foundation  of  the  globe,  an  evidence  of 
wisdom  and  skill  before  which  all  human  ingenuity 
sinks  into  insignificance. 

But  the  most  remarkable  attribute  of  carbon  does 
not  appear  in  this  piece  of  charcoal ;  for  of  all  the 
chemical  elements  carbon  is  by  far  the  most  Protean 
in  its  aspects,  and  charcoal  is  but  one  of  its  many 
manifestations.  In  the  first  place,  there  are  the  nu- 
merous varieties  of  coal,  including  charcoal,  coke, 
lamp-black,  and  bone-black,  all  having  the  same  gen- 
eral properties,  and  most  of  them  partaking  more 
or  less  of  the  structure  of  the  organic  tissues  from 
which  they  were  made.  But,  besides  these  varieties, 
which,  although  differing  so  much  in  their  outward 
aspect,  have  all  essentially  the  same  properties,  there 
are  two  entirely  different  states  of  carbon,  differing 
as  much  from  each  other  and  from  common  charcoal 
as  any  two  solids  possibly  could. 

Are  you  aware  that  the  brilliant  gem  you  prize  so 
highly  is  the  same  chemical  element  as  these  black 
coals?     The  diamond  is  simply  crystallized  carbon, 
8 


170  MODIFICATIONS   OF  CARBON. 

and  although  we  do  not'  know  certainly  how  dia- 
monds are  made  in  the  great  laboratory  of  nature, 
yet  there  is  no  fact  of  chemistry  better  established 
than  this."^  To  those  who  are  not  familiar  with  the 
results  of  modern  chemistry,  it  seems  almost  in- 
credible, and  even  the  chemist  can  hardly  believe 
the  truth  while  he  affirms  it.  It  is  at  utter  vari- 
ance with  the  former  doctrine  of  his  science  ;  it 
cannot  be  reconciled  with  any  of  his  previous  con- 
ceptions, and  constantly  reminds  him  of  the  limi- 
tations of  his  knowledge  and  the  uncertainty  of  his 
philosophy.  And,  turning  to  the  more  familiar  as- 
pects of  the  subject,  how  singular  the  fact,  and  how 
typical  of  the  universality  of  Christian  brotherhood, 
that  He,  who  "  hath  made  of  one  blood  all  nations 
of  men,''  should  have  also  made  of  the  same  ma- 
terial the  priceless  brilliant  which  adorns  the  dia- 
dem of  the  prince,  and  the  soot  which  begrimes  the 
cabin  of  the  humblest  peasant!  How  different  the 
estimation  in  which  these  two  forms  of  carbon  are 
held !  and  yet,  if  the  marks  of  Divine  wisdom  can 
give  nobility  to  a  substance,  the  one  is  as  excellent 
as  the  other. 

But  carbon  exists  in  still  a  third  modification,  dif- 
fering as  much  from  the  diamond  as  that  differs  from 
charcoal.  Every  one  who  has  used  a  common  lead 
pencil  is  familiar  with  graphite,  and  it  is  a  fact  as 
remarkable  as  the  one  just  noticed,  that  the  same 
carbon  which  forms  the  letters  of  a  printed  page  fills 

*  Diamonds  of  minute  dimensions  have,  it  is  stated^  been  lately- 
produced  by  chemical  process. 


DIAMOND,    GRAPHITE,   COAL.  171 

also  the  lines  of  the  pencil  sketch.  Graphite  is  sim- 
ply a  modification  of  charcoal,  and  if  this  fact  is  not 
so  well  known  as  the  humble  relationship  of  the  dia- 
mond, it  probably  arises  from  the  circumstance  that 
graphite  has  been  generally  called  plumbago,  or 
black-lead,  a  misnomer  which  has  given  a  very  er- 
roneous conception  of  its  nature.  Graphite  is  fre- 
quently mixed  with  impurities,  but  it  never  contains 
lead,  and  in  its  finest  condition  it  is  nearly  pure  car- 
bon. Compare  now  graphite  with  the  diamond. 
Could  there  be  two  substances  more  unlike  ?  the  one 
the  softest  of  minerals,  the  other  the  very  hardest ; 
the  one  dull  and  opaque,  the  other  brilliant  and 
transparent.  But  besides  these  external  differences 
they  have  also  a  different  crystalline  form,  a  differ- 
ent specific  gravity,  a  different  capacity  for  heat, 
and,  in  fine,  excepting  that  they  are  both  infusible 
and  combustible,  there  is  not  one  point  of  resem- 
blance between  them.  How  then,  you  will  ask,  do 
we  know  that  they  are  both  the  same  elementary 
substance?  Simply  because,  when  combined  with 
oxygen,  they  both  yield  the  self-same  compound. 

All  three  of  the  modifications  of  carbon  are  com- 
bustible, although  they  take  fire  at  very  different 
temperatures.  Charcoal  will  burn  at  a  red  heat,  the 
diamond  at  a  white  heat,  while  graphite  requires  the 
highest  temperature  which  can  be  attained  by  art. 
But  however  different  may  be  the  temperatures  re- 
quired, the  process  is  the  same  in  all  cases,  and  the 
result  is  the  same.  The  burning  is  simply  combina- 
tion with  the  oxygen  of  the  air,  and  the  result  of 
that   combination   is  carbonic  dioxide  gas.     More- 


172  ALLOTROPISM. 


over,  it  has  been  proved  by  the  most  careful  expe- 
riments that  a  given  weight  of  either  substance 
yields  precisely  the  same  weight  of  carbonic  dioxide. 
Chemically  considered,  then,  the  diamond,  graphite, 
and  charcoal  are  the  same  substance,  although, 
physically  regarded,  no  substances  could  be  more 
unlike.  Chemical  identity,  therefore,  does  not  con- 
sist in  identity  of  properties,  and  we  must  admit 
that  the  same  chemical  element  may  manifest  itself 
under  utterly  different  physical  aspects. 

This  remarkable  phenomenon,  which  has  been 
fully  recognized  only  of  late  years,  has  been  called 
by  chemists  allotropismy^  and  the  diamond,  plum- 
bago, and  charcoal  are  different  allotropic  modifica- 
tions of  the  element  carbon.  Such  differences  of 
manifestation,  moreover,  are  not  confined  to  car- 
bon, nor  are  they  exceptional  occurrences  among 
the  elements.  We  have  already  seen  that  oxygen 
may  exist  in  an  active  and  in  a  passive  modifica- 
tion, which  stand  in  as  striking  antithesis  to  each 
other  as  the  diamond  and  charcoal,  and  the  same  is 
true  of  the  different  conditions  of  sulphur,  phos- 
phorus, and  silicon.  Again,  these  phenomena  are 
not  limited  to  the  elementary  substances,  for  they 
have  been  observed  in  many  compounds  as  well, 
and  every  year  enriches  our  knowledge  with  fresh 
examples.  In  what,  then,  are  such  developments 
to  end  ?  If  substances  so  utterly  unlike  as  the  dia- 
mond, graphite,  and  charcoal  are  merely  modifica- 
tions of  the  same  element,  why  may  not  all  substances 

*  Derived  from  two  Greek  words  signifying  difference  of  condition. 


ALLOTROPISM.  1 73 


be  merely  different  allotropic  states  of  a  few  universal 
principles,  or  possibly  of  only  one  single  essence  ? 
Such,  and  many  similar  questions,  arise  in  the  mind 
of  the  chemist  while  contemplating  these  obscure 
phenomena.  They  cannot  be  satisfactorily  answered 
in  the  present  state  of  chemistry,^  and  they  throw 

*  The  only  explanation  which  we  can  as  yet  give  of  these  phe- 
nomena is  based  on  the  distinction  which  modern  chemistry  makes 
between  the  molecules  of  a  substance  and  the  elementary  atoms  of 
which  these  molecules  themselves  are  made  up.  The  molecules  are 
the  ultimate  particles  in  which  the  qualities  of  a  substance  inhere, 
and  there  are  necessarily  as  many  kinds  of  molecules  as  there  are  dif- 
ferent substances.  But  there  are  only  as  many  kinds  of  atoms  as  there 
are  chemical  elements,  and  the  infinite  variety  of  molecules  is  formed 
by  the  different  combinations  of  the  seventy  kinds  of  elementary 
atoms  now  known,  and  chemical  action  consists  in  the  breaking  up 
of  the  molecules  of  the  substances  which  enter  into  the  chemical 
change  and  the  regrouping  of  their  atoms.to  form  the  molecules  of 
the  substances  which  result  from  it. 

It  is  evident,  from  this  theory,  that  different  molecules — and  hence, 
different  substances — may  result  not  only  from  the  grouping  of  dif- 
ferent atoms,  and  from  the  grouping  of  the  same  atoms  in  different 
proportions,  but  also  from  the  grouping  of  the  same  number  of  the 
same  atoms  in  different  ways.  Thus,  to  take  a  single  example,  four 
atoms  of  carbon,  eight  atoms  of  hydrogen,  and  two  atoms  of  oxygen 
grouped  in  one  way  form  a  molecule  of  butyric  acid,  while  grouped 
in  a  different  way  the  same  atoms  form  a  molecule  of  acetic  ether, 
both  substances  consisting  of  the  same  elements  united  in  the  same 
proportions. 

The  same  principle  may  be  extended  to  the  elementary  substances 
themselves.  They,  like  compound  substances,  are  aggregates  of  mole- 
cules, which  determine  their  properties,  but  these  molecules  consist 
of  atoms  of  one  kind  only.  Diamonds,  graphite,  and  charcoal  are 
distinct  substances,  and  consist,  therefore,  of  different  molecules 
although  in  all  cases  the  molecules  are  formed  from  carbon  atoms 
only.  But  although  every  carbon  atom  in  the  universe  is  exactly  like 
eveiy  other  carbon  atom,  yet  we  may  suppose  that  the  differences  in 


174  ALLOTROPISM. 


a  degree  of  uncertainty  and  doubt  on  its  whole 
philosophy.  I  shall  have  occasion  to  dwell  upon 
this  subject  more  at  -length  in  another  lecture,  and 
have  adduced  the  facts  at  this  time  chiefly  as  further 
illustrations  of  that  fertility  of  resources  which  so 
strikingly  marks  all  the  results  of  creative  skill.  To 
me  this  characteristic  of  the  works  of  nature  is  one 
of  the  most  convincing  evidences  of  divinity.  While 
studying  the  simple  adaptation  of  means  to  ends 
which  we  find  everywhere  around  us,  we  recognize 
in  the  plan  something  analogous  to  the  creations  of 
human  skill,  and  we  almost  feel  a  conscious  relation- 
ship with  its  Author.  But  when  we  consider  this 
incomprehensible  power,  by  which  the  same  ele- 
ment has  been  endowed  with  entirely  different  and 
incompatible  properties,  and  not  only  this,  but  has 
been  adapted  in  each  condition  with  equal  skill  to 
produce  the  most  opposite  and  seemingly  irreconcil- 
able results,  we  are  also  made  to  feel  most  keenly 
that,  although  man  was  created  in  the  image  of  his 
Maker,  he  resembles  the  Divine  Original  only  as  the 
finite  can  resemble  the  Infinite.  *^  For  my  thoughts 
are  not  your  thoughts,  neither  are  your  ways  my 
ways,  saith  the  Lord.    For  as  the  heavens  are  higher 


what  we  have  called  the  three  allotropic  modifications  of  carbon 
result  either  from  the  grouping  of  a  different  number  of  carbon 
atoms  in  each  case,  or  from  the  grouping  of  the  same  number  in  a 
different  way,  or  from  both  causes  combined.  On  account  of  the 
great  hardness  of  the  diamond,  and  its  great  density,  as  compared 
with  the  other  varieties  of  carbon,  it  has  been  assumed  that  the  mole- 
cules of  this  gem  consist  of  a  large  number  of  carbon  atoms  compacted 
together. 


HARD-COAL  FIRE.  1 75 

than  the  earth,  so  are  my  ways  higher  than  your 
ways,  and  my  thoughts  than  your  thoughts/* 

Of  all  the  properties  of  coal,  the  one  with  which 
we  are  most  familiar  is  its  combustibility  ;  and  while 
we  have  been  discussing  its  external  properties,  the 
hard-coal  fire  has  been  built  in  the  grate,  and  it  is 
ready  to  be  lighted.  The  combustion  of  coal  in  one 
or  the  other  of  its  varieties  is  the  great  source  of  all 
the  artificial  heat  used  by  man.  Although  so  entirely 
passive  towards  atmospheric  agents  at  the  ordinary 
temperature,  yet  when  heated  to  a  red  heat  it  takes 
fire  and  combines  with  the  oxygen  of  the  air  with 
great  rapidity.  The  burning  of  coal  is  so  familiar  to 
every  one  that  it  would  seem  hardly  necessary  to 
dwell  upon  the  subject '  here.  But  although  the 
experiment  is  repeated  every  day  in  every  grate 
of  the  city,  and  although  it  has  been  familiar  to  you 
all  from  infancy,  there  are,  nevertheless,  phenomena 
connected  with  it  which  few  have  observed  and  still 
fewer  fully  appreciated.  It  is  a  great  mistake,  but  a 
mistake  too  frequently  made  even  by  scientific  men, 
to  suppose  that  new  knowledge  can  be  gathered 
only  from  the  unexplored  fields  of  science,  when  by 
the  most  familiar  walks  of  life  there  are  countless 
riches  of  truth  which  the  reapers  in  the  hurry  of  the 
harvest  have  passed  unnoticed,  and  which  will 
abundantly  reward  the  careful  gleaners.  In  the 
coal  fire  on  which  you  daily  gaze,  there  is  enough  to 
be  discovered  to  engross  the  attention  of  the  most 
diligent  student  of  nature.  Let  us  see,  therefore,  if 
we,  too,  cannot  learn  something  new,  at  least  to  us, 
from  the  burning  coals. 


176  POINT  OF  IGNITION. 

The  first  fact  to  which  I  would  call  your  atten- 
tion is  the  dfficulty  experienced  in  lighting  coal. 
In  order  to  kindle  the  fire  we  have  placed  on  the 
bottom  of  the  grate,  first,  some  shavings,  then  some 
charcoal,  and,  last  of  all,  the  hard  anthracite  coal. 
We  can  readily  set  fire  to  the  shavings  with  a  match, 
and  they  in  their  turn  will  ignite  the  charcoal ;  but 
it  requires  the  intense  heat  of  the  burning  charcoal 
to  ignite  the  anthracite.  Charcoal  will  not  burn 
unless  at  a  full  red-heat,  and  hard  coal  requires  a 
still  higher  temperature.  But  notice  now  another 
fact :  when  once  inflamed,  the  heat  evolved  by  the 
combination  of  the  carbon  with  oxygen  is  sufficient 
to  sustain  the  temperature  at  the  point  of  ignition. 
Here,  again,  we  see  most  admirably  illustrated  the 
adaptation  of  the  properties  of  the  chemical  elements 
to  entirely  different  ends.  In  order  that  carbon 
might  serve  as  the  solid  substratum  of  all  organized 
beings,  it  was  necessary  that  it  should  be  made  unal- 
terable by  the  air  within  the  limits  of  terrestial  tem- 
perature, but  at  the  same  time  the  economy  of  na- 
ture required  that  it  should  be  made  combustible, 
that  is,  endowed  with  strong  affinities  for  oxygen  ; 
yet  these  affinities  have  been  so  carefully  regulated, 
that  they  are  called  into  play  only  at  a  high  temper- 
ature, and  are  thus  placed  entirely  under  the  con- 
trol of  man. 

Now  that  the  coal  is  in  violent  combustion,  com- 
bining rapidly  with  oxygen,  notice  that  it  burns  en- 
tirely without  flame.  We  have  here  rapid  chemical 
combination,  with  all  the  phenomena  of  active  burn- 
ing, and  yet  no  flame,  simply  because  flame  is  al- 


FLAME   AND   LIGHT.  1 7/ 

ways  burning  gas,  and  in  a  hard-coal  fire  it  is  not 
gas,  but  a  highly  fixed  solid,  that  is  burning.  Char- 
coal and  anthracite  are  almost  the  only  combustibles 
which  burn  in  this  way.  Most  others,  even  when 
naturally  solids,  are  converted  into  gases  at  a  high 
temperature,  and  therefore  burn  with  flame  ;  but  car- 
bon in  all  its  forms,  when  uncombined,  persistently 
retains  its  solid  condition,  even  in  the  hottest  fire. 

Remark,  also,  that  this  combustion  is  attended 
with  a  very  bright  white  light,  and  compare  it  with 
the  more  violent  combustion  of  hydrogen,  with 
which  most  of  the  audience  must  be  familiar. 
Hydrogen  burns  with  a  flame  because  it  is  a  gas ; 
but  this  flame  is  almost  invisible  because  gases,  how- 
ever intensely  heated,  do  not  emit  a  bright  light. 
The  charcoal  burns  without  flame  because  it  is  a 
permanent  solid ;  but  for  this  very  reason  it  emits  a 
great  amount  of  pure  white  light.  So  far,  at  least, 
as  ordinary  experience  extends,  white  light  is  emit- 
ted only  from  ignited  solid  matter.^  Therefore 
neither  white  light  nor  flame  is  a  necessary  concom- 
itant even  of  the  most  rapid  combustion,  the  first 
depending  solely  on  the  solid,  and  the  last  on  the 

*  I  use  the  phrase  white  light  because  an  ignited  gas  or  vapor  may 
emit  a  colored  light,  and  it  has  been  found  that  the  color  is  in  each 
case  determined  by  the  chemical  composition  of  the  ignited  mass  ; 
but  the  light  emitted  from  the  gases  or  vapors  of  which  the  flames  of 
ordinary  combustibles  consist,  is,  at  best,  very  feeble.  The  light  of 
such  flames,  as  will  soon  appear,  comes  almost  entirely  from  solid 
particles  of  charcoal,  and  when  these,  from  any  cause,  are  not  present, 
the  flames  only  yield  a  very  faint,  blue  light.  The  appearance  of 
the  whole  flame  is  then  the  same  as  that  which  may  always  be  seen 
near  the  orifice  of  a  bat-wing  gas-burner. 
8* 


178  INFUSIBILITY   OF  CARBON. 

aeriform,  condition  of  the  burning  substance.  If, 
as  in  the  burning  of  a  candle,  both  flame  and  white 
light  attend  the  process,  it  is  because  both  solid  and 
aeriform  matter  are  there  burning;  and  when  we 
come  to  examine  this  phenomenon  more  closely,  we 
shall  find  that  the  result  is  produced  by  a  most 
delicate  adaptation  of  properties. 

Let  me  next  call  your  attention  to  the  importance 
of  the  infusibility  of  charcoal  in  connection  with  its 
use  as  fuel.  However  high  the  temperature  at 
which  it  burns,  however  intense  the  furnace  heat, 
charcoal  never  loses  its  solid  condition,  and  on  this 
wholly  depends  its  application  for  generating  heat. 
Were  coal  fusible,  even  at  a  very  high  temperature,  it 
would  melt  and  run  out  from  our  grates  and  furnaces, 
and  the  genial  fire  could  not,  as  now,  have  been  lo- 
calized on  the  hearth.  The  enjoyment  of  the  social 
fireside  is  thus  closely  connected  with  a  familiar 
property  of  this  wonderful  element. 

But  our  fire  is  slowly  burning  away,  and  already 
more  than  one-half  of  the  coal  has  been  consumed. 
What  has  become  of  it  ?  Do  you  point  to  the  ashes  ? 
These  are  only  the  earthy  impurities,  which  are 
more  or  less  mixed  with  the  pure  carbon,  and  con- 
stitute but  a  small  fraction  of  the  whole  mass  of  the 
coal.  The  carbon  itself  has  combined  with  the  oxy- 
gen of  the  air  and  formed  a  colorless  and  invisible 
gas,  which  has  escaped  by  the  chimney,  which,  as  I 
have  already  stated  in  the  lecture  on  Oxygen,  is 
called  carbonic  dioxide.  Reflect  now  on  the  im- 
portance of  the  circumstance,  that  this  compound 
of  oxygen  and  carbon  is  aeriform,  and  consider  what 


PRODUCT  OF  COMBUSTION.  1 79 

a  marked  evidence  of  design  and  adaptation  is  to  be 
found  in  the  very  fact  that  the  products  of  ordinary- 
combustion  are  invisible  gases,  which  ascend  our 
chimneys  and  are  wafted  away  by  the  currents  of 
the  atmosphere.  As  common  experience  is  con- 
fined to  the  burning  of  coal,  wood,  oil,  and  similar 
combustibles,  consisting  mainly  of  carbon  and  hydro- 
gen, men  naturally  associate  with  smoke  the  idea 
of  a  gas,  and  are  apt  to  think  that  the  aeriform  con- 
dition is  a  necessary  result  of  the  nature  of  things. 
But  it  is  not  so.  This  peculiar  provision  in  the  case 
of  carbon  and  hydrogen  is  an  exception  to  the  gen- 
eral rule.  The  two  combustible  elements  which  are 
most  closely  allied  to  carbon  in  all  their  properties 
— boron  and  silicon — not  only  form  solids  by  burn- 
ing, but  two  of  the  most  fixed  solids  known  in  nature, 
one  of  which — silica — constitutes,  as  we  have  seen,  at 
least  one-half  of  the  rocky  crust  of  our  globe  ;  and 
the  same  is  true  of  almost  all  the  other  combustible 
elements.  A  very  interesting  experiment  in  illustra- 
tion of  this  fact  may  be  made  by  burning  a  piece  of 
phosphorus  under  a  dry  glass  receiver.  The  smoke 
of  phosphorus  is  solid,  and  it  will  fall  in  thick  white 
flakes,  producing  within  the  glass  the  appearance  of 
a  miniature  snow-storm.  Picture  to  yourself  the 
desolation  which  would  be  produced  were  the  order 
of  nature  so  far  changed  as  to  make  the  products 
of  burning  coal  like  those  of  burning  phosphorus. 
Every  furnace  would  become  a  volcano,  and  we 
should  soon  be  buried  beneath  the  smoke  of  our 
own  fires.  When,  now,  we  consider  that  a  special 
provision   has  been  made  in  the   case  of  that  sub- 


l8o  THE   PRODUCT   HARMLESS. 

stance  whose  combustion  administers  to  our  wants 
by  evolving  light  and  heat,  what  evidence  does  it 
open  to  us  of  the  all-wise  forethought  of  the  Great 
Original ! 

But  this  is  not  all.  Let  me  now  call  your  atten- 
tion to  an  additional  fact  in  regard  to  the  carbonic 
dioxide  which  is  escaping  from  our  coal  fire.  The  gas 
is  entirely  devoid  both  of  odor  and  of  taste,  and, 
moreover,  when  in  a  sufficiently  diluted  condition  it 
can  be  breathed  with  impunity.  Consider  what  an 
amount  of  this  product  is  daily  formed,  and  you  will 
then  be  able  to  appreciate  the  importance  of  this  cir- 
cumstance. The  amount  of  carbonic  dioxide  which 
escapes  from  an  average-sized  iron  blast-furnace  in 
the  course  of  a  single  hour  is  equal  to  at  least  two 
tons,  and  the  amount  which  is  generated  even  by 
our  coal  fire  is  surprisingly  large.  Moreover,  no  less 
than  two  hundred  tons*  of  this  gas  are  breathed 
into  the  air  by  the  population  of  this  city  in  a  single 
day.  If  carbonic  dioxide  had  been  a  pungent  or 
corrosive  gas,  coal  could  not  have  been  used  as  fuel ; 
for  its  combustion,  like  that  of  sulphur,  would  soon 
have  rendered  the  air  irrespirable.  But  so  entirely 
destitute  is  it  of  any  perceptible  odor  or  taste,  that, 
although  it  has  been  evolved  in  these  immense 
quantities  from  every  fire  lighted  by  man  since  he 
appeared  on  the  globe,  it  so  entirely  escaped  no- 
tice that  its  existence  w^as  not  even  suspected 
until  it  was  discovered  by  Dr.  Black  about  a  century 
ago. 

*  Calculated  for  400,000  inhabitants. 


HEAT  EVOLVED.  l8l 


There  is  still  another  remarkable  phenomenon 
attending  a  coal  fire,  which,  although  it  cannot  be 
made  evident  to  the  senses,  has  been  substantiated 
again  and  again  by  the  most  accurate  experiments. 
The  volume  of  carbonic  dioxide  gas  formed  by  the 
combustion  is  exactly  equal  to  the  volume  of  oxygen 
^  consumed.  It  is  a  consequence  of  this  fact,  that 
the  volume  of  the  air  is  not  in  the  slightest  degree 
increased  by  the  vast  quantity  of  carbonic  dioxide 
gas  which  is  daily  poured  into  it.  The  gas  occu- 
pies precisely  the  same  space  as  the  oxygen  re- 
moved during  the  combustion,  and  thus  the  equilib- 
rium of  the  atmosphere  is  not  disturbed.  It  is  true 
that  we  probably  cannot  see  all  the  bearings  of  this 
simple  provision  ;  but  we  know  enough  to  recognize 
in  it  a  most  marked  evidence  of  design. 

The  last  fact  in  connection  with  the  coal  fire  to 
which  I  would  direct  your  attention  is  the  large 
amount  of  heat  which  the  combustion  of  coal  lib- 
erates, and  on  which  its  use  as  fuel  very  largely 
depends.  One  pound  of  charcoal,  in  burning  com- 
pletely, generates  sufficient  heat  to  raise  the  tem- 
perature of  80.8  pounds  of  water  from  the  freezing 
to  the  boiling  point.  Every  pound  of  charcoal  may, 
therefore,  be  regarded  as  containing  sufficient  heat 
to  boil  eighty  pounds  of  ice-cold  water.  What  a 
vast  amount  of  heat  then  lies  buried  in  those  inex- 
haustible beds  of  mineral  coal,  in  which  our  country 
is  so  rich!  And  have  we  not  another  remarkable 
evidence  of  Divine  wisdom  in  the  fact  that  carbon, 
a  substance  which,  on  account  of  its  infusibility  and 
other  qualities,  is  so  well  adapted  for  fuel,  has  been 


1 82  TESTIMONY   OF  BURNING  COALS. 

made  a  great  reservoir  of  heat,  from  which  man  can 
draw  an  unlimited  supply?  When  we  remember 
that  this  heat,  through  the  expansion  of  steam,  may 
be  converted  into  mechanical  force,  and  that  hence 
these  beds  of  coal  are  not  only  magazines  of  heat, 
but  stores  of  force,  which  have  been  accumulating 
from  the  foundation  of  the  globe  for  the  use  of  civ- 
ilized man,  and  when  we  reflect  that  it  is  this  force 
which  is  animating  our  commerce,  weaving  our  cloth, 
forging  our  iron,  and  impelling  the  printing-press, 
how  can  we  express  our  praise  at  the  foresight  of 
that  Providence  which  endowed  coal  with  such 
wonderful  qualities,  made  it  a  vast  repository  of 
heat  and  of  force,  and  then  spread  it  bountifully 
over  the  globe? 

We  have  discovered  all  these  wonderful  indica- 
tions of  design  and  adaptation  in  this  simple  ex- 
periment, so  familiar  as  to  be  almost  trite,  so  fre- 
quently repeated  as  to  pass  unnoticed,  and  they 
are  constantly  speaking  to  us  of  the  great  Au- 
thor of  nature  from  the  fireside  of  every  home, 
and  from  the  furnace  of  every  workshop  in  the 
land.  The  followers  of  Zoroaster  still  worship,  in 
India,  fire  as  divinity,  and  regard  these  burning 
coals  as  sacred.  Behind  this  superstition  and  idol- 
atry there  is  concealed  true  wisdom,  by  which  we 
may  well  profit.  Fire  is  neither  divinity,  nor  yet 
its  emblem.  It  has  no  other  reality  than  as  a  phe- 
nomenon attending  a  chemical  change ;  but  in  the 
qualities  with  which  carbon  has  been  endowed  in 
order  to  produce  this  phenomenon,  in  the  delicate 
adjustment  of  forces  by  which  the  destructive  change 


SOFT  COAL  FIRE.  1 83 

is  confined  within  due  limits,  there  are  indications 
of  divinity  which  may  well  make  us  thoughtful, 
and  consecrate  with  additional  sanctity  the  family 
hearth;  and  if  I  have  succeeded,  however  imper- 
fectly, in  making  audible  to  your  intellectual  ear 
this  mute  eloquence  of  burning  coal,  our  time  has 
not  been  spent  in  vain. 

I  have  thus  far  drawn  all  my  illustrations  from 
the  burning  of  charcoal  and  hard  coal,  simply  be- 
cause these  familiar  forms  of  fuel  are  nearly  pure 
carbon,  and  the  phenomena  attending  their  combus- 
tion are  comparatively  simple.  They  burn,  as  we 
have  seen,  without  flame,  for  the  reason  that  car- 
bon does  not  volatilize,  even  at  the  highest  temper- 
atures. It  is  different,  however,  with  soft  coal,  wood, 
oil,  wax,  and  all  other  combustible  materials  which 
are  used  for  generating  light.  These  do  not  consist 
wholly  of  carbon  ;  but  this  latter  element  is  always 
combined  with  hydrogen,  and  most  of  the  combusti- 
bles named  contain  also,  in  addition,  a  limited  amount 
of  oxygen.  When  heated,  they  all  evolve  common 
illuminating-gas,  and  for  this  reason  burn  with  a 
flame.  In  fact,  the  gas  we  are  burning  here  to- 
night was  made  from  just  such  materials.  If  you 
visit  the  gas-works  of  this  city,  you  will  see  long 
rows  of  iron  retorts,  firmly  built  into  large  brick  fur- 
naces. In  these  retorts  the  gas  is  made,  and  they 
are  connected  by  means  of  a  complicated  system  of 
tubes  with  all  the  numberless  gas-burners  of  this 
large  city.  Every  few  hours  the  retorts  are  charged 
with  soft  coal,  which  soon  becomes  heated  to  a  low 
red  heat.     At  this  temperature  it  slowly  gives  off 


1 84  ILLUMINATING   GAS. 

gas,  and  it  is  the  gas  thus  formed  which  is  now 
illuminating  this  hall.  After  three  or  four  hours,  the 
gas  has  been  all  driven  off,  but  there  is  still  left  in 
the  retorts  the  greater  part  of  the  carbon  of  the 
coal,  in  a  condition  which  is  called  coke.  This  is 
then  removed  and  used  for  feeding  the  furnaces,  and 
a  new  charge  of  soft  coal  is  introduced  in  its  place. 
Coke  is  an  excellent  fuel,  but,  like  charcoal,  it  burns 
without  flame. 

The  processes  which,  in  the  manufacture  and  use 
of  illuminating-gas,  are  spread  over  a  whole  city,  are 
united  in  every  soft-coal  fire.  The  gas  which  is 
burning  at  this  jet  was  generated  in  the  retorts  of 
the  gas-works,  and  brought  here  in  iron  tubes  to  be 
burnt.  In  the  grate  the  gas  is  made  and  burnt  in 
successive  moments,  but  the  process  is  identical  in 
both  cases.  When  you  throw  a  fresh  supply  of  soft 
coal  on  the  grate,  the  first  effect  of  the  heat  is  to 
generate  illuminating-gas,  which  at  once  takes  fire 
and  burns  with  a  brilliant  blaze.  But  after  some 
time  the  flame  ceases,  because  all  the  volatile  ele- 
ments of  the  coal  have  been  expelled,  and  the  coke 
which  is  left  'merely  smoulders,  like  charcoal  or  an- 
thracite. What  is  true  of  soft  coal  is  also  true  of 
wood  and  of  all  this  class  of  combustibles. 

Flame,  as  I  have  before  stated,  is  in  all  cases  burn- 
ing gas.  As  we  are  generally  familiar  with  it,  flame 
is  a  cloud  of  illuminating-gas  combining  on  its  exte- 
rior surface  with  the  oxygen  of  the  air.  In  a  gas  lamp 
the  gas  is  supplied  ready  made  at  the  jet.  In  an  oil 
lamp  or  a  candle,  the  gas  is  manufactured  as  fast  as 
it  burns.     The  use  which  we  make  of  the  flame,  in 


SIMPLE   GAS-FACTORY.  1 85 

all  these  cases,  is  to  generate  light,  and  the  qualities 
of  carbon  have  been  most  admirably  adjusted  to 
produce  that  result.  This  is  the  point  which  I  wish 
next  to  illustrate,  and  we  shall  understand  this  beau- 
tiful example  of  adaptation  more  readily  by  analyz- 
ing the  burning  of  some  one  of  the  light-generating 
materials.  I  will,  therefore,  select  a  common  wax 
candle  as  my  example,  because  it  is  familiar  to 
every  one,  and  illustrates  all  the  points  I  have  in 
view. 

Nothing  could  be  simpler  than  the  candle  itself. 
It  is  a  long  cylinder  of  wax  formed  around  a  string 
made  of  loose  cotton  threads,  which  we  call  the 
wick.  The  wax,  that  familiar  secretion  of  the  honey- 
bee, is  composed,  chemically,  of  carbon,  hydrogen, 
and  a  little  oxygen  ;  the  wick,  as  the  microscope 
would  show  us,  is  merely  a  collection  of  fine  vege- 
table tubes.  Let  us  now  light  the  candle.  For  that 
purpose  we  apply  the  flame  of  a  friction  match  to 
the  end  of  the  wick,  and  mark  the  result.  The  heat 
of  the  match  melts  the  wax  around  the  base  of  the 
wick,  and  now  the  peculiar  virtue  of  these  vege- 
table tubes  come  into  play.  All  fine  tubes  have  the 
power  of  sucking  up  liquid,  and  the  finer  the  tube, 
the  greater  the  height  to  which  the  liquid  is  thus 
elevated.  The  tubes  of  the  wick  act  in  this  way, 
and  the  melted  wax  is  at  once  drawn  up  to  the 
flame  of  the  match.  There  it  is  volatilized  by  the 
high  temperature,  and  a  cloud  of  red-hot  combusti- 
ble gas  forms  around  the  summit  of  the  wick.  Like 
the  rain-drop,  or  any  other  fluid  body  in  a  free  state, 
it  assumes  a  spherical  form,  but  being  much  lighter 


1 86  SIMPLE   GAS-FACTORY. 

than  the  air,  this  sphere  of  gas  no  sooner  forms  than 
it  begins  to  ascend,  and,  being  very  combustible,  is 
burnt  up  by  the  oxygen  of  the  air  with  great  rapid- 
ity, so  that  before  it  has  risen  an  inch  from  the  wick 
it  is  reduced  to  a  point.  Meanwhile,  however,  the 
first  sphere  is  followed  by  others,  which  in  rapid 
succession  meet  with  the  same  fate,  and  at  any 
moment  we  have  a  large  number  of  these  little 
spheres,  one  above  the  other,  rapidly  diminishing  in 
size  from  the  lowest  to  the  highest,  which  has  then 
become  a  mere  point.  Hence  results  the  familiar 
conical  form  of  the  flame.  But  our  match  is  long 
since  burnt  out,  and  what,  you  will  ask,  now  volatil- 
izes the  wax  ?  Solely  the  heat  evolved  by  the  burn- 
ing gas.  This  heat  converts  the  wax  into  vapor  as 
fast  as  it  creeps  up  the  wick,  and  thus  the  flame  being 
constantly  supplied  with  combustible  gas,  the  can- 
dle continues  to  burn  until  it  is  all  consumed.  The 
candle-flame  is,  then,  merely  a  cone  of  volatilized 
wax,  rapidly  combining  on  its  exterior  surface  with 
the  oxygen  of  the  air,  and  as  rapidly  replenished  from 
below  by  the  constant  conversion  of  fresh  wax  into 
vapor.  In  this  process  light  and  heat  are  evolved ; 
but  these  are  generated  solely  on  the  exterior  sur- 
face of  the  flame,  where  the  burning  takes  place. 
Within  it  is  perfectly  dark,  as  can  be  easily  shown 
by  pressing  down  upon  it  a  piece  of  window  glass, 
through  which  the  interior  may  be  seen.  Let  us 
now  study  this  chemical  process  more  carefully, 
as  the  whole  illuminating  power  of  the  flame  de- 
pends on  a  very  delicate  play  of  aflinities. 

The  combustible  gas  formed  from  wax  is  com- 


LIGHT   OF  THE   FLAME.  1 8/ 

posed  essentially  of  charcoal  and  hydrogen.  The 
light  and  combustible  hydrogen  has  so  great  a  ten- 
dency to  retain  its  aeriform  condition,  that,  when 
combined  with  carbon,  it  renders  even  this,  the  most 
fixed  of  all  the  elements,  aeriform ;  but  the  moment 
the  bonds  of  chemical  affinity  are  loosened,  the  car- 
bon resumes  its  solid  condition.  Such  a  change 
takes  place  in  the  flame,  and  it  is  the  particles  of 
solid  charcoal  thus  liberated  that  render  it  lumin- 
ous. Of  the  two  elements  of  the  gas,  hydrogen  has 
the  greatest  affinity  for  oxygen,  and  therefore  burns 
first,  momentarily  setting  free  the  carbon,  which  is 
sprinkled  in  a  fine  powder  through  the  burning  gas. 
This  is  at  once  intensely  heated,  and  each  glov/ing 
particle  becomes  a  centre  of  radiation,  throwing  out 
its  luminous  pulsations  in  every  direction.  The 
sparks  last,  however,  but  an  instant ;  for  the  next 
moment  the  charcoal  is  itself  consumed  by  the  fierce 
oxygen,  now  aroused  to  full  activity,  and  nothing 
but  a  transparent  gas  rises  from  the  flame.  But 
the  same  process  continues ;  other  particles  succeed, 
which  become  ignited  in  their  turn,  and  hence,  al- 
though the  sparks  are  evanescent,  the  light  is  con- 
tinuous. 

Thus  it  appears  that  all  our  artificial  light,  the 
light  which  we  are  enjoying  this  evening,  depends 
upon  this  provision,  by  which  the  particles  of  char- 
coal linger  for  a  moment  in  the  flame  before  they 
are  burnt.  Let  me  again  repeat,  white  light  is  emit- 
ted by  ignited  solid  matter.  The  flame  of  pure  hy- 
drogen gives  very  little  light,  because  there  are  in  it 
no  solid  particles,  and  were  the  affinity  of  oxygen 


LIGHT  OF  THE  FLAME. 


for  carbon  slightly  greater  than  at  present,  the  flame 
of  the  candle  would  be  as  little  luminous :  then  the 
carbon  would  burn  simultaneously  with  the  hydro- 
gen, and  there  would  be  no  pulyerized  charcoal  in 
the  flame  to  radiate  light.  On  the  other  hand,  were 
the  affinity  of  oxygen  for  carbon  a  little  less  than  at 
present,  the  carbon  particles  would  not  burn  in  the 
flame,  but  would  escape  from  it  in  clouds  of  dense 
soot.  Our  Heavenly  Father  has  so  carefully  ad- 
justed the  relative  affinity  of  oxygen  for  the  two  ele- 
ments of  these  light-giving  gases,  that  the  hydrogen 
should  burn  a  small  fractional  part  of  a  second  be- 
fore the  carbon.  During  this  brief  interval  of  time, 
imperceptible  to  our  unaided  senses,  the  solid  parti- 
cles of  charcoal  are  set  free,  become  ignited,  and 
give  motion,  perhaps,  to  a  single  wave  of  light ;  but 
the  instant  after,  they  too  rush  into  combination  with 
the  great  fire-element,  and  not  a  particle  is  left  to  dim 
the  transparency  of  the  air.  The  smallest  variation  in 
either  force  would  destroy  the  adjustment  by  which 
this  result  is  produced,  and  our  lamps  and  candles 
would  cease  to  give  their  light.  How  delicate  the 
adjustment !  How  beneficent  the  result !  How  evi- 
dent the  design ! 

To  me  the  marks  of  God*s  designing  hand  are 
more  conspicuous  in  that  familiar  candle-flame  than 
in  the  grand  cycles  of  astronomy,  or  in  the  wonder- 
ful mechanism  of  the  human  body.  I  return  to  it 
again  and  again  with  renewed  confidence,  and  al- 
ways find  fresh  satisfaction  and  increasing  faith. 
There  are  many  who  believe,  with  Laplace,  that  this 
glorious  system  of  suns  and  planets,  with  all  its 


MARKS   OF  DESIGN.  1 89 

complex  movements  and  adjustments,  might  be 
evolved  out  of  a  nebulous  chaos  by  the  sole  action 
of  the  primary  laws  of  motion  ;  and  now,  after  the 
great  French  mathematician  has  furnished  a  world 
to  begin  with,  a  modern  naturalist  asks  us  to  believe 
that  this  hand  of  mine,  with  all  its  wonderful  com- 
bination of  nerves,  bones,  and  muscles,  was  devel- 
oped out  of  the  claw  of  an  animalcule,  or  some  such 
thing,  by  what  he  calls  ^^  the  law  of  natural  selec- 
tion ;  "  and  although  these  and  similar  theories  may 
be  held  consistently  with  a  belief  in  a  Divine  Dis- 
poser, yet  it  is  too  true  that  to  many  of  their  advo- 
cates the  order  of  nature  signifies  nothing  higher 
than  self-existing  matter,  directed  by  inexorable 
necessity.  But  no  cosmogonist  has  been  able  to  go 
behind  the  chemical  elements,  and  until  human  phi- 
losophy can  show  how  these  forms  of  matter,  with 
all  the  marvellous  adjustments  among  their  prop- 
erties, have  been  evolved  out  of  the  "  star  dust ''  of 
the  original  chaos,  or  out  of  nothing,  and  can  adjust 
by  natural  causes  the  delicate  play  of  forces  in  that 
most  familiar  of  all  phenomena,  a  candle-flame,  it 
will  not  be  able  to  overthrow  the  evidence  of  design 
afforded  by  this  genial  winter-evening  light.  The 
fact  that  these  would-be  world-makers  explain  most 
satisfactorily  what  men  know  least  about,  is,  it 
must  be  confessed,  not  in  favor  of  their  theories. 
Yes,  my  friends,  it  is  these  most  familiar  evidences 
of  design  which  are  the  most  impregnable  against 
the  attacks  of  materialism.  It  is  these  household 
altars  that  we  find  always  burning  to  enlighten 
our    dull    understanding,    to    disperse    our  gloomy 


IQO  SMELTING  OF  ORES. 

doubts,  and  to  reveal  to  us  the  presence  of  our 
God. 

(  The  delicacy  with  which  the  affinity  of  oxygen 
for   carbon    has   been   adjusted  appears  still  more 

/wonderful  when  we  consider  another  of  the  uses  of 
this  force  in  nature.  The  useful  metals,  which  may 
be  said  to  be  the  tools  of  civilized  life,  are  seldom 
found  in  nature  in  a  pure  state.  They  generally 
occur  combined  with  oxygen,  and  this  compound, 
which  is  called  the  ore  of  the  metal,  is  found  in 
beds  or  veins  of  the  rocks,  where  it  has  been  depos- 
ited through  the  agency  of  water.  After  the  miner 
has  dug  out  the  ore  from  the  earth,  and  washed 
it  free  from  impurities,  it  is  the  business  of  the 
smelter  to  melt  out  the  pure  metal.  Now  in  this 
ore  the  metal  is  combined  with  oxygen,  and  unless 
the  smelter  could  break  this  bond,  the  highest  tem- 
perature of  his  furnace  would  be  unavailing.  But 
the  merciful  Parent  of  mankind,  when  he  thus 
locked  up  these  his  choicest  gifts,  gave  to  man  a 
key  which  would  unlock  the  treasure-house,  but  left 
him  to  find  out.  its  use  ;  and  as  in  the  progress  of 
humanity  the  metals  were  required  to  advance 
civilization  and  multiply  the  comforts  of  life,  the 
secret  was  discovered,  and  the  treasures  one  by  one 
were  brought  to  light.  This  needed  key  was  char- 
coal. The  Creator  has  endowed  carbon  with  a  power 
so  strong,  that  it  readily  overcomes  the  force  by 
which  the  metals  are  united  to  oxygen,  and  by 
simply  heating  the  ore  with  charcoal  the  metal  is 
set  free.  Would  that  I  could  give  you  an  idea  of 
the  strength  of  the  force  which  is  required  to  pro- 


SMELTING   OF  ORES,   n      (/  191  ^ 


duce  this  result.  The  affinity  of  carbon  for  oxygen 
is  one  of  the  most  powerful  forces  known  in  nature, 
so  great  as  to  be  immeasurable  by  our  ordinary 
human  standards,  and  yet  it  is  this  same  force  which 
produces  that  delicate  result,  the  light  of  a  candle- 
flame.  With  such  wonderful  skill  does  God  wield 
these  mighty  agents  of  his  power. 

Consider,  finally,  how  this  power  of  reducing  the 
metallic  ores  has  been  united  in  charcoal  to  those 
other  qualities  which  render  it  so  valuable  as  fuel. 
The  smelter  heats  his  furnace  with  the  self-same 
coals  which  reduce  the  ore.  These  coals  remain 
unchanged  in  contact  with  the  ore  until  they  have 
done  their  work,  and  then  are  converted  into  a 
colorless  and  harmless  gas,  which  escapes  by  the 
chimney  and  is  wafted  away  by  the  air;  while,  on 
the  other  hand,  the  melted  metal,  freed  from  its 
long  imprisonment,  flows  out  below  in  glowing 
streams,  ready  to  be  cast  into  thousands  of  useful 
forms. 

Review  now,  for  a  moment,  the  qualities  of  car- 
bon, and  notice  how  manifold  and  important  are  the 
functions  which  this  element  has  been  appointed  to 
subserve.  It  has  been  made  hard  and  brilliant,  for 
the  glazier's  diamond  and  the  monarch's  crown.  It 
has  also  been  made  soft  and  black,  for  the  artist's 
pencil  and  the  printer's  ink.  It  has  been  made 
indestructible  by  atmospheric  agents,  and  thus  has 
preserved  for  us  the  wisdom  of  past  ages,  and  will 
transmit  our  bequests  of  knowledge  to  those  that  are 
to  come.  It  has  been  made  combustible,  and  at  the 
same  time  infusible,  in  order  to  localize  our  fires  and 


192  SUMMARY. 


confine  them  within  their  appointed  bounds.  It  has 
been  made  a  great  reservoir  of  heat,  in  order  that  it 
might  protect  us  from  the  winter's  cold,  and  shed  its 
enlivening  warmth  around  the  family  hearth.  It  has 
been  endow^ed  with  a  strong  affinity  for  oxygen,  in 
order  that  it  might  reduce  the  metallic  ores  ;  but  at 
the  same  time  this  affinity  has  been  so  carefully  ad- 
justed that  the  carbon  particles  linger  in  the  flame 
for  a  moment  before  passing  into  invisible  gas,  and 
thus  become  a  source  of  light  as  well  as  of  heat. 
Lastly,  the  product  of  its  combustion  is  a  gas  so 
transparent  that  it  does  not  even  cloud  the  atmos- 
phere, and  so  bland  that  it  bathes  the  most  delicate 
organisms  without  harm.  What  an  array  of  evi- 
dence have  we  here  !  But  this,  my  friends,  is  only 
the  first  stage  of  that  grand  circulation  of  carbon  in 
nature,  which  we  proposed  to  ourselves  as  our  sub- 
ject this  evening.  The  product  of  all  these  various 
processes  of  combustion  is  carbonic  dioxide,  and  let 
us  now  follow  this  gas  into  the  atmosphere,  and  ex- 
amine some  of  its  more  familiar  qualities. 

Carbonic  dioxide  is  so  perfectly  transparent  and 
so  devoid  of  every  active  quality  that  its  presence 
cannot  be  recognized  by  any  of  our  senses,  and  we 
must  therefore  call  in  the  aid  of  experiment  to  make 
evident  its  existence.  This  is  the  reason  why  it  re- 
mained so  long  unknown,  the  method  we  now  use 
for  detecting  its  presence  having  been  first  discov- 
ered by  Dr.  Black  only  a  little  more  than  a  century 
ago.  The  method  is  very  simple.  Carbonic  dioxide 
has  a  great  tendency  to  combine  with  lime,  and  the 


CARBONIC  DIOXIDE.  I93 

result  of  this  combination  is  the  familiar  white  solid 
called  chalk.  Now  lime  is,  to  a  certain  extent,  solu- 
ble in  water,  while  chalk  is  insoluble ;  and  hence,  if 
lime-water  is  exposed  to  an  atmosphere  containing 
carbonic  dioxide,  the  formation  of  particles  of  chalk, 
rendering  the  transparent  solution  turbid,  will  indi- 
cate the  presence  of  the  gas.  Such  a  result  is  actu- 
ally obtained  by  exposing  lime-water  in  a  saucer  for 
a  few  days  to  the  atmosphere,  and  any  one  can  con- 
vince himself  by  this  simple  experiment  of  the  exist- 
ence of  carbonic  dioxide  in  the  medium  around  us, 
as  well  as  in  the  air  which  is  exhaled  from  the  lungs. 
Indeed,  the  breath  is  so  loaded  with  this  product  of 
combustion  that  lime-water  is  rendered  milky  by 
blowing  into  it  for  only  a  few  minutes.  The  quan- 
tity of  carbonic  dioxide  in  the  atmosphere,  however, 
is  relatively  very  small,  not  amounting  to  more  than 
a  few  ten-thousandths  of  its  whole  weight.  It  en- 
ters to  a  far  greater  extent  into  the  composition  of 
many  rocks.  All  limestones  have  the  same  compo- 
sition as  chalk,  and  contain  nearly  one-half  of  their 
weight  of  carbonic  dioxide,  rendered  solid  by  the 
force  of  chemical  affinity.  These  rocks,  indeed,  are 
the  great  reservoirs  of  this  aeriform  compound,  and 
when  you  consider  how.  widely  the  limestones  are 
distributed,  underlying  whole  districts  of  country, 
reaching  down  to  unknown  depths,  and  piled  up  into 
vast  mountain  chains,  you  can  form  some  apprecia- 
tion of  the  extent  to  which  carbonic  dioxide  gas  was 
used  in  laying  the  foundations  of  the  globe. 

When  pure,  carbonic  dioxide  gas  will  instantly  ex- 
tinguish flame,  and  is  perfectly  irrespirable,  causing 
g 


194  CARBONIC  DIOXIDE. 

the  epiglottis  to  close  spasmodically  and  producing 
immediate  death  by  asphyxia.  When  so  far  diluted 
as  to  admit  of  being  received  into  the  lungs,  it  acts 
like  a  narcotic  poison,  causing  drowsiness  and  insen- 
sibility, and  this  even  when  a  candle  will  burn  in  the 
gas.  Carbonic  dioxide  is  not,  however,  poisonous 
in  the  strict  sense  of  that  term.  On  the  contrary, 
it  is  always  present  in  the  blood  in  large  quantities, 
and  with  it  bathes  all  the  tissues  of  the  body.  The 
carbonic  dioxide  results,  as  we  have  seen,  from  that 
slow  combustion  constantly  going  on  in  the  blood, 
by  which  the  animal  heat  is  maintained,  and  it  is  an 
essential  condition  of  life  that  this  product  should 
be  secreted  from  the  body  as  fast  as  it  is  formed. 
If  the  atmosphere  contains  more  than  a  small  per- 
centage of  the  gas,  the  process  of  secretion  is  arrest- 
ed, and  fatal  results  necessarily  ensue. 

The  density  of  carbonic  dioxide  is  much  greater 
than  that  of  either  of  the  other  constituents  of  the 
atmosphere,  the  same  volume  weighing  one-half  as 
much  again  as  common  air.  Indeed,  it  is  so  heavy 
that  it  .can  be  poured  from  one  vessel  to  another 
like  water,  and  the  immense  volumes  of  carbonic 
dioxide  which  are  constantly  flowing  from  our  lungs 
and  furnaces  would  cover  the  whole  surface  of  the 
earth  with  their  deadly  vapor,  were  it  not  that  the 
Creator  has  provided,  by  those  simple  laws  of  diffu- 
sion, which  we  studied  in  a  former  chapter,  that  this 
noxious  gas  should  be  dispersed  as  fast  as  generated, 
and  so  mixed  with  the  great  mass  of  the  atmosphere 
as  to  be  rendered  harmless  by  extreme  dilution. 
The  unfortunate  accidents  which  sometimes  occur 


CARBONIC   DIOXIDE.  I95 

to  persons  who  descend  incautiously  into  cellars  or 
wells,  where  the  carbonic  dioxide  is  generated  more 
rapidly  than  it  can  be  dissipated,  constantly  remind 
us  that  the  existence  of  animal  life  on  the  globe 
depends  upon  this  beneficent  provision.  The  large 
kilns  in  which  lime  is  burnt  into  quicklime  are  con- 
stantly pouring  out  streams  of  carbonic  dioxide  gas, 
and  more  than  one  poor,  houseless  wanderer,  attracted 
by  the  heat  of  the  kiln,  has  laid  down  to  rest  in  the 
stream,  and  slept  to  wake  no  more.  Were  the  force  of 
diffusion  much  less  than  it  is,  we  should  all  be  con- 
stantly exposed  to  a  similar  fate ;  and  when  we  lie 
dow^n  at  night,  it  is  only  this  guardian  angel  which 
prevents  the  deadly  fumes  of  our  own  fires  from 
descending  on  our  beds. 

Carbonic  dioxide  is  soluble  in  water,  a  given  vol- 
ume of  this  liquid  being  capable  of  absorbing  its 
own  volume  of  the  gas,  irrespective  of  the  tempera- 
ture or  pressure.  We  should  therefore  expect  to 
find  carbonic  dioxide  in  solution  in  all  water  ex- 
posed to  the  air,  and  in  fact  a  cubic  foot  of  river, 
lake,  or  ocean  water  generally  contains  a  very  mucJiT 
greater  amount  of  this  gas  than  an  eqiial  volume  of- 
the  atmosphere.  Water,  when  holding  carbonic  di-? 
oxide  in  solution,  has  its  solvent  power  very  greatly 
increased.  It  then  dissolves,  in  large  quantities,  all 
the  varieties  of  limestone,  and  even  granite  rocks 
cannot  wholly  resist  its  action ;  but  these  solutions, 
when  exposed  to  the  air,  gradually  lose  the  carbonic 
dioxide,  and  with  it  their  solvent  power,  incrusting 
with  calcareous  matter  the  moss,  the  twigs,  or  the 
walls  of  caverns  on  which  the  liquid  may  chance  to 


196  CARBONIC  DIOXIDE. 

rest.  It  is  the  solvent  power  of  such  water,  acting 
slowly  through  ages  of  time,  that  has  hollowed  out 
that  immense  cavern  in  the  limestone  strata  of  Ken- 
tucky, and  it  is  from  the  solution  thus  made  that 
those  stalactitic  ornaments  have  been  formed  which 
add  so  much  to  its  beauty  and  interest.  It  is  also 
this  same  agency  which  in  other  places  has  depos- 
ited beds  of  calcareous  tufa  over  great  areas,  and  ce- 
mented together  loose  sands  into  firm  rocks  ;  and, 
finally,  it  is  from  the  lime  dissolved  in  the  water  of 
the  ocean,  that  the  Crustacea  form  their  shells  and 
the  coral  polyps  build  their  reefs.* 

The  origin  of  carbonic  dioxide  is  the  same  in  wa- 
ter as  in  air.  In  the  water  we  have  not,  of  course, 
active  combustion ;  but  this,  as  has  been  shown, 
is  an  insignificant  source  of  carbonic  dioxide  when 
compared  with  the  never-ceasing  functions  of  res- 
piration and  decay,  and  these  are  as  active  in  the 
rivers,  the  lakes,  and  the  oceans  as  in  the  atmos- 
phere. Moreover,  the  purpose  which  the  carbonic 
dioxide  subserves  is  the  same  in  both  cases,  and 
this  demands  our  attentive  study. 

I  have  already  intimated  that  carbonic  dioxide  is 
one  of  the  few  articles  of  which  the  food  of  plants 
consists.  Let  us  trace,  for  a  moment,  the  history  of 
the  plant.  The  seed  containing  the  germ  is  placed 
in  the  soil.  The  genial  warmth  of  the  sun  calls  it 
into  activity,  and   it  shoots  forth  its  small  leaflets 

*  The  whole  peninsula  of  Florida  has  been  in  great  measure  built 
up  by  these  little  animals  with  the  lime  rock  which  the  waters  of  the 
Mississippi  pour  into  the  Gulf,  and  which  has  been  dissolved  from 
the  lime  deposits  of  our  Western  States. 


FOOD   OF  PLANTS.  I97 

into  the  air.  For  a  short  time  the  small  stock  of 
starch  and  similar  nourishment  stored  in  the  seed  by 
a  wise  Providence  serves  for  its  support ;  but  this  is 
soon  exhausted,  and  for  the  future  the  plant  must 
depend  for  its  food  upon  the  soil  and  upon  the 
air.  The  articles  which  compose  its  diet  are  exceed- 
ingly simple.  They  are  water,  carbonic  dioxide,  and 
ammonia,  substances  always  present  in  the  atmos- 
phere and  in  every  fertile  soil.  As  soon  as  the 
young  plant  has  expanded  its  green  leaves  it  ab- 
sorbs these  substances,  partly  through  its  root- 
lets from  the  soil,  and  partly  through  its  leaves 
from  the  air.  The  leaf,  a  tissue  of  minute  organic 
cells,  is  the  laboratory  in  which,  from  these  few 
compounds,  are  elaborated  the  different  organs  of 
the  plant.  The  sun's  rays,  acting  upon  the  green 
parts  of  the  leaf,  give  them  the  power  of  absorb- 
ing water,  carbonic  dioxide,  and  ammonia,  and  of 
constructing  from  the  materials  thus  obtained  the 
woody  fibre,  starch,  sugar,  and  other  compounds 
of  which  the  plant  consists.  We  have  analyzed  the 
woody  fibre,  and  we  know  that  it  is  composed  of 
carbon  and  water.  Twenty-seven  ounces  of  wood 
contain  twelve  ounces  of  carbon  and  fifteen  ounces 
of  water.  Moreover,  the  amount  of  carbon  re- 
quired to  make  twenty-seven  ounces  of  wood  is 
contained  in  forty-four  ounces  of  carbonic  dioxide. 
If,  then,  we  add  together  forty-four  ounces  of  car- 
bonic dioxide  and  fifteen  ounces  of  water,  and 
subtract  from  this  sum  thirty-two  ounces  of  oxy- 
gen, we  shall  have  just  the  composition  of  wood. 
This  is  what  the  sun's  light  accomplishes  in  the 


198  FOOD   OF  PLANTS. 

leaves  of  the  plant.  It  decomposes  the  carbonic 
dioxide,  and  unites  its  carbon  to  the  elements  of 
water  to  form  the  wood. 

What  I  have  stated  to  be  true  of  wood  is  equally 
true  of  starch,  gum,  sugar,  and  most  of  the  products 
of  vegetable  life.  All  these,  with  a  few  exceptions, 
which  I  shall  notice  in  the  next  lecture,  are  pre- 
pared by  the  plant  from  carbonic  dioxide  and  water, 
under  the  influence  of  the  sun*s  light.  Why  it  is 
that  starch  is  deposited  in  the  cells  of  the  potato, 
sugar  in  those  of  the  sugar-cane,  and  gum  and  woody 
fibre,  more  or  less,  in  all  plants,  we  do  not  know. 
These  are  the  mysteries  of  organic  life  which  no 
science  has  been  able  to  solve.  This  much,  however, 
is  certain.  The  acorn,  buried  in  the  ground,  grows 
into  the  noble  oak.  Of  that  wide-spreading  tree,  at 
least  nine-tenths  consist  of  carbon  and  water.  The 
water  is  absorbed,  as  such,  directly  from  the  atmos- 
phere ;  the  carbon  was  recovered  from  the  carbonic 
dioxide  decomposed  by  the  sun's  rays.  Here  is  the 
wonderful  fact.  The  gentle  influences  of  the  sun- 
beam have  the  power  of  reversing  the  process  of 
combustion,  of  overcoming  the  intense  affinity  of  the 
fire-element,  tearing  it  apart  from  the  carbon,  and 
restoring  it  to  the  air.  How  great  this  power  is,  I 
have  already  endeavored  to  illustrate.  I  have  stated 
that  the  affinity  of  oxygen  for  carbon  is  one  of  the 
strongest  affinities  known  to  nature,  immeasurable 
by  any  human  standard.  In  order  to  decompose 
carbonic  dioxide  in  our  laboratories,  we  are  obliged 
to  resort  to  the  most  powerful  chemical  agents,  and 
to  conduct  the  process  in  vessels  composed  of  the 


BURNING   REVERSED.  1 99 

most  resisting  materials,  under  all  the  violent  mani- 
festations of  light  and  heat,  and  we  then  succeed  in 
liberating  the  carbon  only  by  shutting  up  the  oxy- 
gen in  a  still  stronger  prison  ;  but  under  the  quiet 
influences  of  the  sunbeam,  and  in  that  most  delicate 
of  all  structures,  a  vegetable  cell,  the  chains  which 
unite  together  the  two  elements  fall  off,  and  while 
the  solid  carbon  is  retained  to  build  up  the  organic 
structure,  the  oxygen  is  allowed  to  return  to  its 
home  in  the  atmosphere.  There  is  not  in  the  whole 
range  of  chemistry  a  process  more  wonderful  than 
this.  We  return  to  it  again  and  again,  with  ever- 
increasing  wonder  and  admiration,  amazed  at  the 
apparent  inefficiency  of  the  means,  and  the  stupen- 
dous magnitude  of  the  result.  When  standing  be- 
fore a  grand  conflagration,  witnessing  the  display  of 
mighty  energies  there  in  action,  and  seeing  the  ele- 
ments rushing  into  combination  with  a  force  which 
no  human  agency  can  withstand,  does  it  seem  as  if 
any  power  could  undo  that  work  of  destruction,  and 
rebuild  those  beams  and  rafters  which  are  disap- 
pearing in  the  flames  ?  Yet  in  a  few  years  they  will 
be  rebuilt.  This  mighty  force  will  be  overcome ; 
not,  however,  as  we  might  expect,  amidst  the  con- 
vulsion of  nature,  or  the  clash  of  the  elements,  but 
silently,  in  a  delicate  leaf  waving  in  the  sunshine. 
And  this  is  not  all.  Those  luminous  waves  which 
beat  upon  the  green  surface  of  the  leaf  are  there 
arrested,  and  their  moving  power  so  completely 
absorbed,  that  the  reflected  rays  will  not  even  affect 
the  exquisitely  sensitive  plate  of  the  photographer. 
But  the  power  of  the  light  has  not  been  lost,  and 


200  ORIGIN   OF  COAL. 

when  the  wood  is  burnt  and  the  carbon  converted 
back  into  carbonic  dioxide,  this  power  reappears 
undiminished  in  the  heat  which  radiates  from  the 
burning  embers.  The  heat,  therefore,  which  the 
wood  contains,  and  which  it  gives  forth  on  burning, 
comes  from  the  sun.  What  a  beautiful  provision  of 
Providence  have  we  here !  During  the  summer, 
when  the  sun  is  warming  us  with  his  genial  rays,  he 
is  also  laying  up  in  the  growing  wood  vast  stores  of 
heat,  with  which  to  warm  us  at  the  winter  evening 
fireside,  when  his  rays  have  been  withdrawn. 

But  you  will  tell  me,  it  is  not  wood,  it  is  coal 
which  is  burning  in  the  grate,  and  you  will  lead  me, 
perhaps,  to  the  mouth  of  some  black  coal-pit,  and 
ask  if  those  dismal  regions  below  ever  saw  the  sun. 
Certainly!  and  it  is  one  of  the  most  remarkable 
revelations  of  modern  science,  that  the  stone-like 
coal  was  once  alive.  Coal  is  the  remains  of  an 
ancient  vegetation,  which  flourished  on  the  earth 
ages  before  man  first  walked  in  Eden.  The  process 
by  which  it  has  been  formed  and  buried  in  the  earth 
is  well  known.  You  can  see  it  now  forming  in  many 
tropical  swamps.  There  you  will  find  a  vast  mass 
of  vegetable  matter,  the  result  of  a  rank  vegeta- 
tion, gradually  decaying  under  water.  The  land  is 
slowly  sinking,  and  as  this  bed  of  peat  sinks  with 
it,  it  becomes  covered  with  mud  and  sand,  which 
numerous  streams  are  constantly  washing  into  the 
swamp.  Thisgoes  on  year  after  year,  century  after 
century,  age  after  age,  until  the  bed  is  buried  hun- 
dreds of  feet  beneath  the  surface.  In  the  meantime 
the  vegetable  tissues  undergo  a  sort  of  internal  com- 


ORIGIN   OF   COAL.  201 

bustion,  similar  to  that  which  takes  place  in  a  char- 
coal mound.  Wood  consists,  you  will  remember,  of 
carbon  and  the  elements  of  water.  The  oxygen 
which  it  contains  reacts  on  the  carbon  and  hydro- 
gen. Carbonic  dioxide  and  water  are  formed,  which 
escape,  while  the  rest  of  the  hydrogen  and  carbon 
unite  together  to  form  the  coal.  The  reaction  is  a 
true  process  of  combustion,  and  the  heat  thus 
evolved  aids  the  chemical  change,  and  gives  to  the 
coal  its  baked  appearance.  This  change  it  requires 
long  ages  to  complete.  Millions  and  millions  of 
times  has  the  earth  repeated  its  annual  revolution 
around  the  sun,  and  the  whole  external  appearance 
of  the  globe  has  changed  since  those  mighty  forests 
grew,  which  have  been  petrified  in  the  coal.  But 
though  such  long  intervals  have  elapsed,  their  his- 
tory has  not  been  lost.  It  has  been  written  on  the 
rocks,  the  mighty  monuments  of  past  ages.  The 
geologists  have  read  it,  and  we  know  with  as  much 
certainty  the  form  of  the  leaves  and  the  structure  of 
the  stems  of  those  ancient  trees,  as  we  do  those  of 
the  oak  or  the  chestnut.  We  know,  also,  that  every 
atom  of  coal  which  now  lies  buried  hundreds  of  feet 
beneath  the  surface  was  once  a  part  of  the  atmos- 
phere, and  that  the  heat  which  it  evolves  by  burn- 
ing was  received  from  the  sun,  when  the  carbonic 
dioxide  was  decomposed  by  the  light  in  the  leaves  of 
the  ancient  trees.  Consider  for  a  moment  of  what 
immense  value  to  man  are  those  beds  of  coal. 
Without  them  modern  civilization  would  have  been 
impossible.  Remember  that  since  the  dawn  of  crea- 
tion  the   sun  has  been  employed  in  accumulating 

9* 


202  PREPARATION  FOR  MAN. 

these  vast  stores  of  force,  and  thus  preparing  the 
globe  for  civilized  man.  We  may  admire  the  genius 
of  a  Papin  and  a  Watt,  who  have  told  us  how  to  use 
this  force,  and  who  have  thus  covered  the  ocean 
with  steamships  and  the  land  with  railways;  but 
let  us  not  forget  that  infinitely  greater  wisdom  which 
saw  the  end  from  the  beginning,  and  before  the 
mountains  were  brought  forth,  or  ever  the  continents 
were  formed,  laid  up  the  beds  of  coal  in  the  early 
strata,  and  preserved  them  through  the  long  ages  of 
geological  time  until  the  earth  had  become  fitted  to 
be  the  abode  of  man. 

I  have  now  glanced  at  some  of  the  distinctive 
features  of  the  great  circulation  of  carbon  in  nature, 
and  have  endeavored  to  show  that  the  sun's  rays 
are  the  prime  moving  power  of  the  whole.  I  trust 
that  you  have  been  impressed  with  the  grandeur  of 
its  cycles,  the  delicacy  of  its  adjustments,  and  the 
mighty  power  of  that  mysterious  influence  by  which 
it  is  sustained ;  but  above  all,  that  I  have  succeeded 
in  making  clear  to  your  intellectual  vision  those 
marks  of  wisdom  and  of  power  which  have  been  so 
visibly  stamped  upon  this  Divine  economy. 


CHAPTER    VII. 

TESTIMONY  OF  NITROGEN. 

In  order  to  complete  my  very  imperfect  sketch  of 
the  wonderful  adaptations  which  the  various  qualities 
and  functions  of  our  atmosphere  present,  I  wish  in 
my  lecture  this  evening  to  examine  with  you  the 
properties  of  nitrogen  gas.  This  aeriform  substance 
is  the  chief  constituent  of  the  air,  making  up  no  less 
than  four-fifths  of  its  entire  mass,  and,  although  so 
seemingly  inert,  discharges  functions  no  less  impor- 
tant than  those  of  oxygen  gas  to  the  well-being  of 
man.  Nitrogen  is  not,  however,  like  oxygen,  an  ele- 
ment widely  distributed  in  nature,  and  entering  as  a 
chief  constituent  into  the  composition  of  the  globe. 
The  atmosphere  is  the  only  great  reservoir  of  nitro- 
gen, and  to  this  and  to  the  bodies  of  organized  beings 
its  presence  is  almost  exclusively  confined.  It  seems 
to  be  the  essential  element  of  all  the  higher  forms  of 
corporeal  vitality,  and  it  is  frequently  called  the  zoo- 
gen,  or  life-generator.  By  some  mysterious  process  it 
is  constantly  being  withdrawn  from  the  atmosphere, 
and  entering  into  the  composition  of  the  numberless 
living  forms  which  clothe  the  earth  with  verdure  and 
crowd  it  with  animal  life  ;  but  these  forms  soon  pass 

203 


204  LIMITED  DIFFUSION. 

away,  and  by  the  inevitable  process  of  decay  the  ni- 
trogen is  restored  to  the  great  reservoir  from  which 
it  was  originally  withdrawn.  Science  has  not,  as  yet, 
been  able  to  follow  all  the  steps  of  this  remarkable 
process ;  but,  nevertheless,  enough  is  known  to  show 
that  the  properties  of  nitrogen  have  been  most  ad- 
mirably adapted  to  the  numerous  important  ends 
which  it  has  been,  appointed  to  subserve. 

Nitrogen  is,  then,  peculiarly  the  element  of  the 
atmosphere.  It  not  only  constitutes  the  greater 
part  of  the  aerial  ocean,  but  it  exists  there  in  a  per- 
fectly free  and  uncombined  condition,  and — with 
the  self-limiting  exception  just  noticed — is  found 
nowhere  else.  We  should  naturally  expect  to  find 
in  nitrogen  gas,  occupying  so  important  a  place  as  it 
does  in  the  scheme  of  creation,  a  substance  full  of 
the  highest  interest.  Yet  nothing  could  be  less  invit- 
ing than  its  external  properties.  A  permanent  gas, 
even  at  the  lowest  temperatures,  without  color  or 
odor,  it  is  entirely  devoid  of  every  active  property. 
It  will  extinguish  a  candle  immersed  in  it,  and  will 
not  sustain  animal  life :  but  these  are  merely  negative 
qualities ;  for  animals  cannot  live  in  an  atmosphere 
of  nitrogen,  solely  because  it  does  not  contain  oxy- 
gen, and  it  will  not  support  combustion  because  it  is 
not  endowed  with  active  affinities.  Moreover,  in  all 
other  outward  aspects  nitrogen  is  equally  inert.  It 
exerts.no  action  whatever  upon  the  most  delicate 
chemical  compounds,  and,  with  a  few  unimportant 
exceptions,  will  not  enter  into  direct  combination 
with  any  of  the  chemical  elements.  Consider  also 
the  nitrogen  as  it  exists  in  the  atmosphere.     Al- 


SINGULAR  INERTNESS.  205 

though  in  immediate  contact  with  the  most  violent 
of  the  elements,  and  exposed  to  its  action  when  in  its 
fiercest  state,  under  the  varying  influences  of  light, 
heat,  and  electricity,  yet  no  combination  between 
the  two  results,  except  to  a  very  limited  extent, 
and  under  pecuHarly  oblique  conditions.  Through 
an  ordinary  iron  blast-furnace  there  pass,  in  the 
course  of  a  single  day,  many  tons  of  this  mixture 
of  nitrogen  and  oxygen  called  air.  The  oxygen,  as 
we  know,  causes  the  most  violent  chemical  action; 
but  although  the  nitrogen  is  brought  into  contact 
with  the  same  intensely  heated  coal  and  iron,  no 
combination,  at  least  of  any  importance,  ensues. 

Shall  we  then  conclude  that  nitrogen  is  entire- 
ly unendowed  with  chemical  affections, — that  it  is 
capable  of  forming  no  compounds,  and  of  produc- 
ing no  powerful  effects, — that  it  is,  in  fine,  a  mere 
dead  weight  in  the  atmosphere,  placed  there,  for 
the  want  of  something  better,  to  fill  up  the  void 
and  to  give  the  required  density,  as  a  ship  is  fre- 
quently loaded  with  ballast  when  there  is  a  lack  of 
freight?  Such  is  the  conclusion  to  which  the  ap- 
pearances would  naturally  lead,  and  such  is  the  con- 
clusion at  which  the  chemists  arrived  in  the  early 
stages  of  their  inquiry.  Yet  no  inference  could  be 
more  at  variance  with  actual  facts;  for  so  far  is  it 
from  true  that  nitrogen  is  the  uninteresting  sub- 
stance which  these  negative  qualities  would  seem 
to  indicate,  that  there  are  but  few  elements  which 
form  a  larger  number  of  compounds,  or  which  are 
endowed  with  more  varied  powers  when  the  neces- 
sary conditions  of  combination  are  fulfilled.     Nitro- 


206  BALLAST  OF  THE  ATMOSPHERE. 

gen  can  be  made  to  unite  with  the  other  elements 
only  by  indirect  and  circuitous  processes.  It  is  one 
of  its  most  distinctive  qualities  to  avoid  direct  com- 
bination;  but  when  the  necessary  conditions  are 
present,  it  surprises  us  by  the  readiness  with  which 
it  combines,  and  by  the  great  variety  and  remark- 
able character  of  the  resulting  compounds.  When 
we  should  least  expect  it,  we  find,  not  single  com- 
pounds, but  whole  classes,  springing  into  existence, 
which,  while  they  often  defy  our  investigations  by 
their  Protean  and  'complex  character,  yet  in  other 
cases  excite  our  admiration  by  the  simplicity  of 
their  constitution  and  by  the  beauty  of  the  plan 
according  to  which  they  have  all  been  fashioned. 
The  points,  then,  which  especially  characterize  ni- 
trogen, and  in  which  the  evidences  of  design  in  its 
constitution  are  to  be  traced,  are,  first,  its  unex- 
ampled inertness  when  in  a  free  condition ;  sec- 
ondly, the  variety  and  remarkable  nature  of  its  com- 
pounds ;  thirdly,  the  peculiarly  oblique  processes  by 
which  all  these  compounds  are  formed ;  and,  lastly, 
their  very  great  instability. 

Nitrogen  may  be  very  appropriately  termed  the 
ballast  of  the  atmosphere,  and  this  is  undoubtedly 
the  most  obvious  of  its  functions.  Air,  you  will  re- 
member, is  not,  in  any  proper  sense  of  the  term,  a 
distinct  substance.  It  is  a  mixture  of  several  sub- 
stances, or  rather  there  coexist  around  the  globe  at 
least  three  different  atmospheres — one  of  nitrogen, 
one  of  oxygen,  one  of  aqueous  vapor,  and  perhaps 
we  should  add,  as  a  fourth,  one  of  carbonic  dioxide 
— each  with  its  own  peculiar  characteristics,  and  so 


BALLAST  OF  THE  ATMOSPHER^^.  "tlC^j 

entirely  distinct  that  it  would  ret^in^^^its  essential 
properties  were  the  rest  removed." -^.Agai<y  when/' >, 
studying  in  our  fifth  lecture  the  general  feature^' pf 
the  great  aqueous  circulation  on  the  earth,  we  dtsi  / 
covered  that  the  whole  plan  turns  on  the  fact  that  "  I. 
the  atmosphere  of  aqueous  vapor  is  mixed  with  a 
large  mass  of  other  aeriform  matter,  which  moderates 
all  atmospheric  changes  and  mitigates  the  violence 
of  their  effects.  It  also  appeared  in  the  third  lecture 
that  the  atmosphere  of  oxygen  had  been  subjected 
to  a  similar  restraint,  and  that  the  aroused  energies 
of  this  terrible  destroyer  had  been  most  carefully 
tempered  by  great  dilution.  As  the  atmosphere  is 
constituted,  the  oxygen  cannot  reach  the  burning 
combustible  without  carrying  with  it  the  whole  mass 
of  the  surrounding  air ;  but  if  this  mass  of  aeriform 
matter  were  not  present,  the  devouring  element 
would  rush  upon  its  prey  with  a  fury  which  nothing 
could  withstand,  and  iron^  would  burn  as  readily 
as  straw.  Moreover,  in  several  other  connections 
we  have  shown  that  it  is  an  essential  condition  in 
the  scheme  of  terrestrial  nature  that  the  air  should 
have  its  actual  density.  See  now  how  beautifully  all 
the  conditions  are  fulfilled  in  the  atmosphere.  The 
proportion  of  oxygen  has  been  most  carefully  ad- 
justed to  the  necessities  of  animal  life,  and  made  so 
small  that  the  violence  of  the  fire-element  may  be 
restrained  within  due  limits.  The  amounts  of  aque- 
ous vapor  and  of  carbonic  dioxide  have  in  like  man- 
ner each  been  accurately  adjusted  to  the  purposes 

*  An  iron  watch-spring  burns  with  the  greatest  readiness  in  a  jar 
of  pure  oxygen  gas. 


208  SPECIAL   RELATIONS. 

which  they  were  appointed  to  subserve,  and  then,  in 
order  to  make  up  the  required  density,  a  large  mass 
of  a  perfectly  inert  gas  has  been  added.  Thus  in  the 
very  inertness  of  nitrogen  we  find  the  most  obvious 
evidence  of  adaptation.  Its  negative  qualities  are 
precisely  those  required  in  a  substance  which  is 
designed  to  act  as  so  much  dead  material,  adding  to 
the  density  of  the  atmosphere  without  interfering 
with  the  functions  of  its  active  agents. 

Consider,  also,  how  very  greatly  this  evidence  of 
design  is  enhanced  by  the  fact  that  nitrogen  is  found 
only  in  the  atmosphere  and  in  the  bodies  of  organ- 
ized beings,  into  which  it  has  been  temporarily  with- 
drawn. It  is  not,  like  oxygen,  carbonic  acid,  or 
water,  a  main  constituent  of  the  globe,  and  cannot 
therefore  be  regarded,  as  the  fatalists  would  have  us 
believe,  as  so  much  material  left  over  after  the  solid 
globe  had  been  condensed  by  the  molecular  forces 
from  a  chaotic  nebula.  Nitrogen  is  not  only  exactly 
adapted  to  the  functions  it  subserves  in  the  atmos- 
phere, but,  moreover,  these  are  its  only  uses,  and  I 
cannot  see  how  it  is  possible  to  resist  the  conclusion 
that  it  was  especially  designed  for  the  place  it  fills. 
That  you  may  appreciate  the  strength  of  this  evi- 
dence, let  me  illustrate  the  subject  by  an  example 
from  common  life,  which  will  be  more  to  our  pur- 
pose than  a  philosophical  analysis  of  the  argument 
itself. 

It  does  not  follow  that  the  square  granite  blocks 
which  form  the  greater  part  of  the  front  of  yonder 
magnificent  warehouse,  however  well  adjusted  they 
may  be,  were  actually  cut  with  reference  to  this 


STRENGTH   OF  THE   EVIDENCE.  209 

building,  although  the  strong  presumption  is  that 
they  were.  Nor  does  it  follow  that  those  highly- 
ornamented  window-caps  and  that  elaborate  cornice 
were  originally  designed  for  this  particular  edifice, 
although  the  presumption  that  such  was  the  case  is 
still  stronger  than  before.  Nay,  more,  it  is  not  even 
absolutely  certain  that  those  skilfully  carved  orna- 
ments which  adorn  the  front,  and  are  built  into  the 
walls,  were  originally  intended  to  be  placed  where 
they  are,  although  to  doubt  this  conclusion  would 
be  the  extreme  of  incredulity.  I  admit,  it  is  barely 
possible  that  they  were  originally  made  for  another 
building,  rejected,  perhaps,  for  some  defect,  and 
afterwards  put  up  here.  But  I  will  show  you  where 
there  is  an  evidence  of  design  in  the  building-mate- 
rial of  this  warehouse  which  you  will  be  forced  to 
accept.  It  is  not  conspicuous,  and  might  be  over- 
looked. Just  here  at  the  corner  of  the  building 
there  is  a  very  peculiarly  shaped  block  of  stone. 
You  never  saw  one  like  it  before.  This  extraordi- 
nary shape  was  required  by  the  peculiar  form  of  the 
building  lot  and  the  position  of  the  walls  on  the  ad- 
joining estate.  The  sides  of  the  lot  are  not  perpen- 
dicular to  the  front,  and  the  block  has  been  cut  to 
the  precise  angle  of  the  bevel,  and  at  the  same  time 
exactly  fits  the  adjacent  walls.  The  conclusion  that 
this  block  was  designed  for  that  place  is  irresistible. 
No  sane  mind  would  doubt  it  for  a  moment.  I  do 
not  say  there  is  not  one  chance  in  many  millions, 
estimated  on  the  doctrine  of  probabilities,  that  a 
block  of  this  exact  size  and  shape  might  have  been 
found  among  the  refuse  stock  of  the  stone-cutter's 


2IO  STRENGTH   OF  THE  EVIDENCE.     . 

yards ;  but  I  do  say,  that,  in  the  absence  of  absolute 
proof  to  the  contrary,  the  certainty  that  this  granite 
block  was  wrought  with  reference  to  the  place  it  fills, 
and  that  the  exact  correspondence  of  its  dimension 
and  angles  was  the  result  of  measurement,  is  as  great 
as  it  is  possible  to  attain  by  any  process  of  reasoning 
short  of  a  mathematical  demonstration;  moreover, 
it  is  as  great  as  can  be  obtained  in  physical  science, 
or  in  any  department  of  human  knowledge  one  step 
removed  from  the  facts  of  consciousness  or  of  obser- 
vation. 

The  evidence  that  nitrogen  was  designed  for  the 
place  which  it  fills  in  the  atmosphere  is  vastly 
stronger  than  this.  The  force  of  the  argument  in 
the  illustration  just  cited  evidently  increases  very 
rapidly  the  more  singular  the  shape  of  the  granite 
block,  and  the  more  accurately  its  form  has  been 
adjusted  to  the  place  it  fills.  Now  nitrogen  is  as 
unique  among  the  chemical  elements  as  water  is 
among  the  compounds.  Its  external  properties  are 
so  entirely  different  from  those  even  of  the  class  of 
elements  to  which  it  belongs,  that  chemists  can 
hardly  believe  that  it  is  a  simple  substance,  and  for 
the  last  fifty  years  have  been  vainly  attempting  to 
decompose  it ;  but  it  has  resisted  all  their  efforts, 
and  the  more  intimately  they  have  become  ac- 
quainted with  its  properties,  the  more  singular  and 
exceptional  it  has  appeared.  At  the  same  time, 
while  presenting  these  remarkable  anomalies,  nitro- 
gen has  been  fitted  to  the  unique  place  which  it  fills 
in  the  scheme  of  creation,  with  a  nicety  and  pre- 
cision which  it  is  as  much  beyond   our  powers  of 


STRENGTH   OF  THE   EVIDENCE.  211 

thought  to  conceive,  as  it  is  beyond  my  feeble  lan- 
guage to  describe.  It  is  not  only  that  one  or  two  of 
the  corners  of  this  block  of  nature's  edifice  have  been 
bevelled  to  an  exact  angle,  but  it  has  been  adjusted 
at  every  point  to  the  ten  thousand  conditions  of 
that  comple:?^,  structure  I  have  been  imperfectly 
describing  during  this  course  of  lectures,  with  a 
skill  immeasurably  beyond  all  human  art,  and  with 
an  intelligence  which  "  looketh  to  the  ends  of  the 
earth  and  seeth  under  the  whole  heaven."  If  this 
be  so, — and  you  will  find  that  my  guarded  expres- 
sions fall  far  short  of  the  truth, — why  not  use  in 
these  matters  of  faith  the  same  common  sense 
which  w^e  apply  with  so  much  success  in  common 
life,  and  which  in  our  daily  intercourse  it  would 
be  nothing  short  of  madness  to  disregard?  We 
do  not  hesitate  to  trust  the  skill  and  honesty  of 
a  fellow-man,  whom  we  not  only  have  never  seen, 
but  even  as  to  whose  character  our  sole  evidence  is 
the  most  indefinite  testimony.  Why,  then,  not  ac- 
cept the  precious  and  comforting  truths  of  religion, 
and  repose  equal  faith  in  the  providence  of  our 
Heavenly  Father,  on  evidence  which,  we  must  ad- 
mit, is  ten  thousand-fold  stronger,  and  when  we 
have  everything  to  gain,  and  nothing  to  lose  ?  Is  it 
said.  There  is  still  room  for  doubt  ?  Of  course  there 
is.  God  be  thanked  !  there  is  no  relation  in  life  in 
which  there  is  not  doubt.  Were  there  no  doubt, 
there  would  be  no  faith,  no  trust,  no  confidence,  no 
love ;  the  heart  would  be  absorbed  in  the  intellect, 
religion  would  become  an  axiom,  and  morality  a 
formula  of  mathematics.     Use  but  one-half  of  the 


212  STRENGTH   OF  THE   EVIDENCE. 

observation,  one-half  of  the  inteUigence,  which  are 
never  at  fault  in  the  business  of  life,  and  these  marks 
of  the  Creator's  wisdom  and  providence  which  lie  all 
around  us  will  become  as  evident  as  the  sun.  Act 
on  this  evidence,  and  the  door  of  grace  will  be 
opened,  new  light  will  stream  into  th^  soul,  and  all 
nature  will  be  seen  radiant  with  a  Father's  love. 

All  this  striking  evidence  of  design  and  adapta- 
tion we  have  discovered  in  the  most  obvious  of  the 
attributes  of  nitrogen, — in  those  merely  negative 
qualities  in  virtue  of  which  it  increases  the  density 
of  the  atmosphere  without  interfering  with  the  func- 
tions of  its  active  constituents.  It  would  not,  how- 
ever, be  in  accordance  with  that  economy  of  resources 
which  we  find  everywhere  in  nature,  that  the  uses 
of  nitrogen  should  be  limited  to  this  single  object ; 
and  after  what  we  have  already  seen  to  be  true  in  the 
case  of  oxygen,  we  shall  not  be  surprised  to  find 
this  singular  element  suddenly  changing  its  char- 
acter and  appearing  in  a  new  condition.  The  sec- 
ond point,  as  you  will  rem.ember,  which  I  am  to 
illustrate  in  regard  to  nitrogen,  is  the  variety  and 
remarkable  nature  of  its  compounds,  as  well  as 
the  singularly  oblique  processes  by  which  they  are 
formed ;  and,  having  examined  the  marks  of  design 
it  bears  in  its  first  manifestations,  let  us  now  study 
the  no  less  impressive  evidence  presented  by  the 
second.  It  would  be  entirely  out  of  place  in  a 
popular  work  like  the  present,  to  describe  in  de- 
tail any  of  the  countless  nitrogenized  compounds 
which  are  known  to  chemistry,  and  it  would  re- 
quire a  separate  volume   merely  to   illustrate   the 


COMPOUNDS   OF  NITROGEN.  21 3 

characteristic  features  of  the  great  classes  into  which 
they  may  be  subdivided.  I  shall  be  able  only  to 
glance  at  a  few  general  facts  which  illustrate  the 
point  now  under  discussion,  and  also  the  part  which 
nitrogen  plays  in  organic  nature. 

Although  nitrogen  presents  such  an  indifferent 
exterior  towards  the  oxygen  of  the  atmosphere,  it 
can,  nevertheless,  be  made  to  combine  with  it  by 
resorting  to  certain  oblique  processes,  and  there 
may  thus  result  no  less  than  five  different  com- 
pounds. Every  one  is  familiar  with  that  highly 
corrosive  liquid  called  nitric  acid,  and  this  is  formed 
by  the  union  with  water  of  one  of  the  compounds 
in  question.  Under  certain  conditions  this  acid  re- 
sults from  the  union  of  the  oxygen,  nitrogen,  and 
aqueous  vapor  which  are  mixed  together  in  the  air. 
Indeed,  the  only  essential  difference  between  the 
bland  atmospheric  air  and  this  highly  active  chem- 
ical agent  consists  in  the  fact  that  while  in  air  the 
elements  are  only  mixed  together,  in  the  acid  they 
are  chemically  combined.  Were  nitrogen  to  be 
suddenly  endowed  with  the  active  affinities  which 
from  its  position  among  the  chemical  elements  we 
might  naturally  expect  it  to  possess,  then  nitric 
acid  would  be  formed  in  the  atmosphere  in  large 
quantities,  and  it  is  only  the  unexampled  inertness 
of  nitrogen  which  prevents  a  result  which  would  be 
fatal  to  all  organic  life.  But  although  so  corrosive 
when  pure,  nitric  acid  when  immensely  diluted  is 
one  of  the  few  materials  which  nourish  and  sustain 
the  plant,  and  therefore  provision  has  been  made 
that  it  should  be  formed  in  the  atmosphere,  but 


214  HOW   PRODUCED. 


only  under  very  restricted  conditions,  and  to  a  very 
limited  extent.  When  electrical  sparks  are  passed 
through  a  confined  quantity  of  air,  in  the  presence 
of  some  alkaline  substance,  such  as  potash,  soda,  or 
lime,  a  very  partial  combination  takes  place  between 
the  two  elements,  and  an  infinitesimal  quantity  of 
nitric  acid  is  formed.  So,  also,  when  organic  matter 
decays  in  the  presence  of  these  same  alkalies,  a  sim- 
ilar combination,  although  to  a  very  slight  extent, 
results.  Nitric  acid  is  endowed  with  such  violent 
affinities  that  it  doiSs  not  remain  in  a  free  state.  It 
at  once  enters  into  combination  with  the  alkalies, 
forming  a  class  of  salts,  of  which  saltpetre  is  the 
best  known  example,  and  from  which  the  com- 
mon nitric  acid  is  extracted  for  the  uses  of  the  arts. 
Nitrogen,  you  will  notice,  acts  here  very  much  like 
a  self-willed  child.  All  the  powers  of  nature  cannot 
compel  it  to  combine  directly  with  oxygen  ;  but  if 
you  offer  to  it  these  alkalies  as  an  inducement,  and 
make  your  approaches  sufficiently  indirect,  you  can 
coax  it  to  combine,  and  nitric  acid  is  then  formed. 
We  do  not  understand  how  the  peculiar  conditions 
just  mentioned  conspire  to  produce  the  result ;  but 
the  whole  phenomenon  seems  to  be  mysteriously 
connected  with  ozonized  oxygen,  and  is  undoubt- 
edly another  phase  of  that  obscure  subject,  allotrop- 
ism,  to  which  we  alluded  in  a  previous  lecture.  See 
now  how  beautifully  this  attribute  of  nitrogen  has 
been  adapted  to  the  conditions  of  vegetable  life, 
and  made  the  means  by  which  the  plant  is  furnished 
with  one  of  the  articles  of  its  food.  Every  discharge 
of  lightning  is  accompanied  by  a  partial  combina- 


COMPOUNDS   OF  NITROGEN  21 5 

tion  of  the  elements  of  the  atmosphere,  and  the 
nitric  acid  which  is  thus  formed  and  washed  down 
by  the  rain-water  serves  to  fertihze  the  soil  and 
bring  the  growing  corn  to  maturity.  So  in  like  man- 
ner, when  life  is  extinct,  and  the  organized  forms  are 
resolved  into  their  original  elements,  the  very  pro- 
cess of  decay  causes  a  similar  combination,  and  thus 
sweetens  the  flowers  which  spring  from  the  grave. 

But  not  only  does  nitrogen  combine  with  oxygen. 
It  unites  also  with  hydrogen,  that  element  which  is 
the  very  antithesis  of  oxygen,  and  forms  a  most 
remarkable  compound  called  ammonia.  This  sub- 
stance is  the  very  reverse  of  mtrrc^acid  in  all  its 
chemical  relations,  but,  like  nitric  acid,  it  is  a  highly 
active  and  caustic  agent.  I  need  not  dwell  upon 
this  fact ;  for  the  common  smelling-bottle  has  made 
every  one  familiar  with  this  pungent  substance. 
Nitrogen  manifests  the  same  indifference  towards 
hydrogen  that  it  does  towards  oxygen,  and  the  two 
elements  can  be  made  to  unite  only  by  indirect  pro- 
cesses, which  are  not  well  understood.  The  most 
important  of  these  is  the  process  of  decay.  This 
destructive  change  in  all  the  higher  forms  of  organ- 
ized beings  is  attended  with  the  formation  of  am- 
monia, and  the  same  nitrogenized  compound  is  a 
uniform  result  of  the  normal  functions  of  animal  life. 
You  will  not,  therefore,  be  surprised  to  learn  that 
traces  of  ammonia,  as  of  nitric  acid,  are  found  in  the 
atmosphere  and  in  all  rain-water.  Indeed,  it  is  gen- 
erally supposed  that  the  two  are  in  combination, 
forming  a  salt  called  nitrate  of  ammonia,  but  the 
amount  present  is,  at  best,  very  small. 


2l6  HOW  PRODUCED. 

Ammonia  is  thought  by  many  to  be  a  more  im- 
portant article  of  vegetable  diet  than  nitric  acid ; 
but  our  knowledge  of  agricultural  chemistry  is  very 
imperfect,  and  chemists  are  not  agreed  on  many  of 
the  most  fundamental  points."^  Still,  as  I  have 
before  stated,  nitrogen  is  an  essential  element  of  all 
the  higher  forms  of  corporeal  vitality,  and  compounds 
like  those  we  have  been  considering  are  the  ap- 
pointed channels  by  which  it  is  introduced  into  the 
organization  of  the  plant.  Had  these  compounds 
been  allowed  to  form  to  any  extent  in  the  atmos- 
phere, they  would  soon  have  rendered  the  globe 
uninhabitable.     It  was  therefore  essential  that  nitro- 

*  Since  this  book  was  written,  it  has  been  stated  by  several  investi- 
gators that  the  chief  nitrogen  compound  in  the  atmosphere  and  in 
rain-water  is  nitrite  of  anwionia^  which  differs  from  the  nitrate  of 
ain?nonia  mentioned  above  only  in  containing  a  smaller  proportion  of 
oxygen.  Whether  the  last  is  also  normally  present  does  not  yet 
appear,  and  to  what  extent  the  one  or  the  other  may  be  concerned  in 
the  processes  of  vegetable  growth,  has  not  been  determined.  From 
one  point  of  view,  nitrite  of  ammonia  may  be  regarded  as  composed 
of  nitrogen  gas  and  water,  and  some  chemists  believe  that  it  is  formed 
by  the  direct  union  of  these  two  substances,  and  that  this  union  is 
favored  by  the  processes  of  evaporation,  combustion,  and  decay 
which  are  constantly  going  on  in  the  atmosphere.  This  theory  is 
certainly  supported  by  many  facts,  and  those  who  hold  it  generally 
believe  that  nitrite  of  ammonia  is  the  chief,  if  not  the  sole,  source 
from  which  the  plants  derive  their  supply  of  nitrogen,  while  others 
attach  only  a  secondary  importance  to  the  recent  experiments.  If  the 
theory  is  correct,  the  foraiation  of  nitrite  of  ammonia — the  presence 
of  which  in  surface-water,  and  in  the  soil,  under  certain  conditions,  is 
beyond  doubt — would  be  the  natural  result  of  the  subsequent  union 
of  nitrite  of  ammonia  (formed  as  just  described)  with  the  oxygen  of 
the  air ;  but,  as  intimated  above,  the  whole  subject  is  still  very 
obscure,  and  from  any  experiments  yet  made  we  should  not  be  justi- 
fied in  drawing  definite  conclusions. 


PECULIAR  INSTABILITY.  21/ 

gen  should  be  endowed  with  that  unexampled  inert- 
ness which  it  manifests  in  its  gaseous  state.  But 
had  not  at  the  same  time  a  power  of  combination, 
under  certain  restricted  conditions,  been  granted, 
this  chemical  element  would  not  only  have  been  an 
isolated  phenomenon  in  nature,  an  exception  to  its 
general  laws,  but  its  usefulness  would  have  been 
restricted  to  the  least  remarkable  of  its  functions. 
Unlike  the  results  of  human  skill,  this  creation  of 
Divine  wisdom  has  been  adapted  to  the  most  varied 
and  apparently  incompatible  ends  ;  and  while  in  the 
atmosphere  it  is  a  mere  dead  weight,  it  is  also  the 
most  plastic  of  the  elements,  is  capable  of  entering 
into  the  most  complex  relations,  and  thus  serves  as 
the  peculiar  substratum  of  all  the  higher  forms  of 
organized  being. 

-  The  last  point  I  am  to  illustrate  in  regard  to  ni- 
trogen is,  perhaps,  the  most  characteristic  of  its  fea- 
tures, and  it  is  one  on  which  its  relations  in  the 
scheme  of  organized  nature  very  greatly  depend. 
All  the  compounds  of  nitrogen  are  very  unstable, 
and  the  slightest  force  is  generally  sufficient  to  over- 
power the  delicate  affinities  by  which  the  elements 
are  held  together,  when  the  nitrogen  at  once  returns 
to  its  home  in  the  atmosphere.  Although  this  inert 
element  may  be  coaxed  into  combination,  it  never 
forms  strong  compounds.  Its  affinities,  although  so 
varied,  are  at  best  very  feeble  and  delicate.  It  is 
always  a  weak  timber  in  a  chemical  structure,  and 
when  this  timber  breaks,  as  it  certainly  will,  sooner 
or  later,  the  whole  falls.  You  will  need  no  further 
illustration  of  this  fact  than  to  be  told  that  gunpow- 


2l8  PRONENESS  TO  DECAY. 

der,  percussion-powder,  and  gun-cotton  are.all  nitro- 
genized  compounds,  and  oweTKeTr  well-known  prop- 
erties to  the  weak  affinities  of  this  element.  Nitric 
acid  is  only  a  little  more  stable  than  these  explo- 
sive agents,  and  ammonia,  although  one  of  the  most 
permanent  of  nitrogenized  compounds,  is  still  very 
easily  decomposed.  Passing  next  to  organized  sub- 
stances, we  find  this  distinguishing  character  still 
more  conspicuous.  As  we  have  already  seen,  it  is 
always  the  nitrogenized  compounds  which  start  the 
decay  in  vegetable  or  animal  structures ;  and  thus 
the  great  characteristic  feature  of  all  organized  mat- 
ter, its  proneness  to  change  and  decay,  nay,  even 
death  itself,  is  clearly  foreshadowed  in  the  proper- 
ties of  nitrogen.  When  the  Creator  first  endowed 
this  element  with  its  feeble  affinities,  He  also  passed 
the  doom  of  all  living  creatures :  ^^  Dust  thou  art, 
and  unto  dust  shalt  thou  return." 

Here  I  must  leave  this  division  of  my  subject.  It 
would  be  highly  interesting  to  study  the  innumer- 
able phases  in  which  nitrogen  manifests  itself  in  the 
world  of  living  matter;  to  trace  how,  under  the 
guidance  of  that  mysterious  principle  of  life,  the 
mpst  complex  organic  compounds  are  educed  from 
such  simple  materials  as  water,  carbonic  dioxide, 
ammonia,  and  nitric  acid ;  to  follow  these  nitrogen- 
ized compounds  through  their  varied  history,  from 
the  time  they  are  first  generated  in  the  plant  until 
they  are  incorporated  into  the  brain,  the  muscles, 
and  the  bones  of  man ;  to  notice  at  every  stage  the 
same  instability  which  so  strikingly  characterizes  all 
the  compounds  of  this  singular  element,  capable  of 


CIRCULATION   OF  NITROGEN.  219 

existing  only  under  the  continued  influence  of  the 
vital  principle,  and,  when  that  ceases  to  act,  gradu- 
ally degenerating  and  falling  back  into  the  simple 
products  from  which  they  sprang ;  but  all  such  de- 
tails would  be  incompatible  with  the  plan  of  these 
lectures,  and  must  therefore  be  reluctantly  passed 
by.  If,  however,  I  have  been  able  to  place  before 
you  in  a  clear  light  the  main  features  of  this  remark- 
able element,j^its  isolated  existence  in  the  atmos- 
phere, its  unparalleled  inertness  in  the  aeriform  con- 
dition, its  power  of  combination  under  restricted 
conditions,  the  great  variety  and  complexity  of  its 
compounds,  and,  finally,  their  singular  proneness  to 
decomposition  and  decay ,-\it  is  all  that  I  could  ex- 
pect. We  have  seen  thatin  each  of  these  respects 
nitrogen  has  been  adapted  with  exquisite  skill  to 
the  unique  part  which  it  plays  in  the  scheme  of  the 
world  ;  and  this  element,  although  outwardly  so  un- 
attractive and  dull,  has  borne  the  richest  testimony 
to  the  wisdom  of  the  Maker. 

Having  now  become  acquainted  with  the  charac- 
teristic features  of  nitrogen,  let  us  next  consider  the 
part  which  this  element  plays  in  that  grand  circula- 
tion of  matter  in  organic  nature,  which  has  been  al- 
ready in  part  described.  I  have  before  stated  that 
the  plant  is  a  true  apparatus  of  reduction,  in  whose 
leaves  carbonic  dioxide  is  decomposed  hy  the  solar 
light.  The  plant  absorbs  carbonic  dioxide  partly 
through  its  leaves  from  the  air,  and  partly  through 
its  roots  from  the  soil.  The  sun's  rays,  acting  upon 
the  green  surface  of  the  leaf,  decompose  in  some 


220  THE   PLANT  A   PRODUCER. 

mysterious  way  the  carbonic  dioxide,  overcoming 
the  intense  affinities  of  its  elements,  fixing  the  car- 
bon, and  setting  free  the  oxygen,  to  be  restored  to 
the  air.  From  the  carbon  thus  obtained,  and  from 
the  water,  ammonia,  and  nitric  acid  which  are  the 
other  articles  of  its  food,  together  with  a  few  inor- 
ganic salts,  the  plant  constructs  its  tissues.  If  in 
their  production  carbonic  dioxide  and  water  alone 
take  part,  there  result  such  substances  as  woody 
fibre,  starch,  gum,  and  sugar,  and  of  these  nine- 
tenths  of  all  vegetable  structures  consist.  If  the 
nitrogen  compounds  are  likewise  employed  in  tfie 
process,  there  are  formed,  besides,  suchnitrogenized.- 
products  as  albumen,  caseine,  and  fibrine.  These 
last  names  may  not  be  so  familiar  to  you  as  the  first, 
but  you  are  equally  familiar  with  the  substances, 
and  will  recognize  them  at  once  when  told  that  the 
white  of  an  egg  is  nearly  pure  albumen,  that  cheese 
consists  almost  entirely  of  caseine,  and  meat  of 
fibrine.  Although  these  substances  are  best  known 
to  us  as  animal  products,  they  are  likewise  found  in 
all  those  vegetables  which  are  articles  of  food.  Al- 
bumen and  caseine  can  readily  be  extracted  from 
either  peas  or  potatoes,  and  gluten,  the  substance 
which  gives  tenacity  to  flour-paste,  has  essentially 
the  same  composition  as  animal  fibrine. 

The  animal,  unlike  the  plant,  has  not  the  power 
of  forming  the  substance  of  its  tissues  from  inor- 
ganic compounds,  but  it  receives  them  ready  formed 
from  the  vegetable  kingdom.  It  transmutes  the 
vegetable  products  into  a  thousand  shapes  in  order 
to  adapt  them  to  its  uses,  but  its  peculiar  province 


THE  ANIMAL  A   CONSUMER.  221 

is  to  assimilate  and  consume,  not  to  produce.  The 
nitrogenized  compounds  just  referred  to  are  the 
portion  of  its  food  which  suppHes  the  constant  waste 
attending  all  the  vital  processes.  The  non-nitro- 
genized  starch  and  sugar,  although  they;  form  the 
greater  part  of  our  food,  are  never  actually  incorpo- 
rated into  the  tissues  of  the  body,  and,  as  we  have 
already  seen,  are^  merely  the  fuel  by  which  its  tem- 
P^erature  is  maintained.  The  animal  may  either  re- 
ceive its  nitrogenized  food  directly  from  the  plant, 
as  is  the  case  with  all  herbivora,  or  only  indirectly^ 
like  the  carnivora  ;  but  in  either  case  the  origin  is 
the  same,  and  by  the  process  of  digestion  these, 
originally  at  least,  vegetable  products  are  assimilated 
and  converted  into  bones,  muscles,  or  nerves,  as  the 
necessities  of  the  animal  may  require.  We  find  that 
during  this  process  these  substances  do  not  undergo 
any  fundamental  change,  but  merely  become  parts 
of  more  finely  organized  tissues.  We  discover  in 
the  blood  albumen  and  caseine,  having  precisely  the 
same  composition  as  that  which  may  be  prepared 
from  potatoes,  and  the  substance  of  the  muscle 
does  not  differ  essentially  from  the  gluten  of  flour- 
meal.. 

Do  not,  however,  suppose  that  the  part  played  by 
the  animal  is  less  noble  than  that  of  the  plant.  It  is 
really  much  higher.  We  must  be  careful  to  make 
a  distinction,  too  frequently  overlooked,  between 
the  organized  structure  and  the  material  of  which  it 
consists.  There  is  the  same  difference  here  as  be- 
tween a  house  and  the  bricks  of  which  it  is  built. 
It  was  formerly  supposed  that  organic  matter  was 


222  MATTER  AND   ORGANISM. 

formed  under  peculiar  influences,  and  subject  to 
special  laws.  But  it  is  now  known  that  animal  and 
vegetable  substances  obey  the  same  laws  of  affinity 
as  mineral  matter,  and  the  recent  progress  of  chem- 
istry has  given  us  great  reason  to  believe  that  we 
may  be  able  one  day  to  prepare  all  the  materials  of 
which  plants  and  animals  build  their  cells.  Here, 
however,  chemistry  stops  and  creation  begins.  The 
great  Architect  of  nature  alone  can  fashion  this  dead 
material  into  living  forms."^  The  vegetable  kingdom 
is  a  great  laboratory,  in  which  the  sun's  rays  manu- 
facture from  the  gases  of  the  atmosphere,  and  from 
a  few  earthy  salts  of  the  soil,  the  different  materials 
which  the  organic  builders  employ.  There  the  bricks 
are  made,  and  from  these  the  animal  builds  his  bones 
and  muscles.  He  does  not  make  the  bricks,  but  he 
does  what  is  far  more  glorious,  he  builds  with  them 
his  delicate  frame,  and  as  the  work  of  the  builder  is 
higher  than  that  of  the  brick-maker,  so  in  the  scale 
of  being  is  the  animal  higher  than  the  plant,  and  the 
more  noble  in  proportion  as  its  structure  is  more 
intricate  and  elaborate. 

While  the  plant  is  a  true  apparatus  of  reduction, 
the  animal  is  a  true  apparatus  of  combustion,  in 
which  the  substances  it  has  derived  from  the  vegeta- 
ble are  burnt  and  restored  to  the  atmosphere  in  the 

*  I  do  not  forget  the  alleged  facts  of  spontaneous  generation  ;  but 
even  after  the  very  extended  investigations  of  the  last  ten  years,  it 
may  still  be  stated  as  the  general  result  of  the  innumerable  experi- 
ments which  have  been  made,  that,  in  no  case  has  even  the  lowest 
type  of  an  organic  cell  been  produced  from  unorganized  matter,  unless 
through  the  natural  processes  of  growth  from  a  pre-existing  germ. 


ORIGIN   OF  MUSCULAR  POWER.  223 

form  of  carbonic  dioxide,  water,  and  ammonia,  ready 
to  be  again  absorbed  by  the  plant  and  to  repass 
through  the  phases  of  organic  life.  Our  bodies  are 
furnaces,  —  furnaces  continually  burning,  —  whose 
fuel  is  our  flesh,  and  whose  smoke  is  the  breath  of 
our  nostrils.  Every  time  I  strike  a  blow  a  portion 
of  the  muscle  is  consumed,  actually  burnt  up  in 
producing  the  force.  In  every  muscular  effort  I 
make,  in  every  word  I  utter,  in  every  step  I  take, 
a  portion  of  the  muscles  concerned  is  burnt,  and 
motion  can  no  more  be  produced  in  the  animal 
body  without  a  combustion  of  its  tissues,  than  it  can 
be  generated  in  a  steam-engine  without  burning  fuel 
under  its  boiler.  As  in  the  steam-engine  the  burning 
fuel  is  the  source  of  its  power,  so  in  the  animal  body 
the  burning  muscle  is  the  immediate  cause  of  all  its 
motions.  I  will  to  strike  a  blow,  but  my  will  is  not 
the  moving  power.  The  power  is  in  the  muscle,  and 
in  the  exertion  the  muscle  is  consumed.  The  muscle, 
however,  does  not  originate  the  motion,  any  more 
than  the  fuel  originates  the  motion  of  the  steam- 
engine.  The_Riel,  we  have  seen,  does  not  originate 
heat.  It  is  merely  a  reservoir  of  heat,  and  in  burn- 
ing it  merely  givesup  the  heat  it  once  received  from 
the  sun.  So  the  muscle  is  merely  a  reservoir  of 
force,  and  in  burning  it  gives  out  the  force  it  con- 
tains. The  force  it  contains  it  also  received  from 
the  sun,  when  its  substance  was  formed  by  the  sun's 
rays  acting  upon  the  leaves  of  the  plants. 

What  a  wonderful  revelation  is  this !  Muscular 
power  originates  in  the  sun.  We  do  not  create  the 
force ;  we  do  not  originate  it ;  we  merely  excite  it. 


224  THE  ANIMAL   MACHINE. 

The  force  which  originally  came  from  the  sun  lies 
dormant  in  the  muscles  until  our  will  calls  it  into 
activity.  Our  bodies  are  machines,  perfect  ma- 
chines it  is  true,  but  yet  machines.  Like  all  other 
machines,  they  merely  transmit  power,  they  cannot 
create  it.  They  very  closely  resemble  a  steam-en- 
gine. As  we  must  constantly  feed  the  engine  with 
fuel,  so  we  must  supply  our  bodies  with  food  in  or- 
der to  repair  the  muscle  burnt,  and  we  can  no 
more  be  said  to  originate  that  force  which  mani- 
fests itself  in  our  bodies,  than  the  stoker,  who  shov- 
els the  fuel  into  the  grate,  can  be  said  to  originate 
the  force  of  the  steam-engine.  We  are  not  our  bod- 
ies, although  we  live  in  them,  and  direct  their  mo- 
tions. They  move  by  forces  which  emanate  from  a 
source  far  higher  than  we,  and  we  stand  in  the  same 
relation  to  them  in  which  an  engineer  does  to  his 
machine.  Certainly  Lavoisier,  the  great  father  of 
modern  chemistry,  had  caught  a  glimpse  of  the  re- 
sults which  it  was  left  for  more  modern  science 
to  establish,  when  he  wrote :  "  Organization,  sensa- 
tion, voluntary  motion,  life,  only  exist  on  the  surface 
of  the  earth,  and  in  places  exposed  to  the  light.  It 
might  be  said,  indeed,  that  the  fable  of  Prometheus 
was  an  expression  of  a  philosophical  truth,  which 
had  not  escaped  the  penetration  of  the  ancients. 
Without  light,  nature  were  without  life  and  without 
soul ;  a  beneficent  God,  in  shedding  light  over  cre- 
ation, strewed  the  surface  of  the  earth  with  organi- 
zation, with  sensation,  and  with  thought." 

Although  it   thus   appears   that   our  bodies   are 
mere   channels    of   force,   machines  whose    motive 


MIND   CONTROLS   THE   MACHINE.  22$ 

power  emanates  from  the  great  centre  of  the  solar 
system,  let  us,  while  we  recognize  this  startling  re- 
sult of  science,  remember  the  no  less  certain  fact  of 
consciousness, — that  we  are  not  our  bodies,  though 
we  live  in  them, — that  this  conscious  personality  is 
something  entirely  apart  from,  and  infinitely  superior 
to,  these  corporeal  atoms  in  which  it  is  temporarily 
enshrined,  surviving  as  it  does  all  their  changes.  Let 
us  also  keep  clearly  in  view  the  still  more  glorious 
truth,  that  this  machine,  with  all  its  infinite  capabil- 
ities of  good  and  evil,  is  put  entirely  at  our  com- 
mand ;  that  not  one  conscious  motion  can  take  place 
unless  we  will  it ;  and  that  this  will  of  ours  can  set 
in  action  a  chain  of  causes  which  no  space  can  bound 
and  no  time  can  limit.  Let  us  then  well  consider 
how  great  is  the  power  which  has  thus  been  dele- 
gated to  us,  let  us  duly  weigh  the  awful  responsi- 
bility it  involves,  and  so  act  that,  when  the  Master 
claims  his  own,  we  may  not  be  ashamed  to  render  up 
the  account  of  our  stewardship. 

Moreover,  although  it  is  true  that  these  bodies 
themselves  are  constantly  dissolving  into  air,  that 
the  material  atoms  w^hich  compose  them  will  in  a  few 
short  weeks  all  be  gone,  and  that  there  is  nothing 
but  the  shadow  of  our  forms  which  we  can  call  our 
own,  we  must  also  remember  that  there  is  a  myste- 
rious principle  within,  constantly  renewing  and  re- 
pairing our  wasting  frames, — a  cunning  architect 
superintending  a  thousand  builders  who  are  con- 
stantly reconstructing,  with  materials  prepared  by 
vegetation,  the  bones,  the  muscles,  and  the  nerves, 
as  fast  as  they  are  wasted  and  consumed;  making, 

lO* 


226  THE  VITAL  PRINCIPLE. 

in  a  most  mysterious  way,  beyond  all  human  com- 
prehension, here  the  fibre  of  a  muscle,  there  the  fila- 
ment of  a  nerve,  here  building  up  a  bone,  there  unit- 
ing a  tendon,  fashioning  each  with  scrupulous  nicety, 
and  fitting  each  to  its  place  with  never-failing  skill. 
But  no  sooner  is  the  work  of  the  architect  done,  than 
another  great  power  comes  in  to  destroy  it.  The 
oxygen  gas  which  the  blood  absorbs  in  the  lungs  and 
carries  to  the  different  parts  of  the  body  burns  up 
these  carefully  elaborated  tissues,  converting  them 
into  carbonic  dioxide,  water,  and  ammonia,  which 
pass  into  the  atmosphere,  from  which  they  originally 
came.  Life  is,  in  fact,  a  constant  struggle  between 
the  builders  and  the  destroying  element  of  the  air; 
and  when  its  short  term  is  ended,  and  the  builders 
cease  because  they  are  wearied  and  few,  then  ''  the 
dust  returns  to  the  earth  as  it  was,  and  the  spirit  re- 
turns unto  God  who  gave  it." 

But  let  us  not  sorrow  as  those  who  have  no  hope ; 
"  for  we  know  that  if  our  earthly  house  of  this  tab- 
ernacle were  dissolved,  we  have  a  building  of  God, 
an  house  not  made  with  hands,  eternal  in  the  heav- 
ens." And  cannot  He  who  hath  clothed  us  with 
our  earthly  house  provide  for  us  a  better  and  more 
enduring  mansion?  and  are  not  all  these  wonderful 
changes  in  our  present  bodies  a  foreshadowing  of 
the  final  consummation,  when  our  earnest  desire  '^  to 
be  clothed  upon"  shall  be  satisfied,  and  "  mortality 
shall  be  swallowed  up  of  life  "  ? 

Such  is  a  very  imperfect  sketch  of  that  great  cycle 
of  changes,  of  which  all  organic  nature  is  merely  a 
passing  phase.     Let  us  review  for  a  moment  its  main 


THE   ORGANIC   CYCLE.  22y 

features.  When  the  foundations  of  the  globe  were 
laid,  there  were  collected  in  the  atmosphere  all  the 
essential  elements  of  organized  beings.  From  this 
inexhaustible  storehouse  the  plant  absorbs  water, 
carbonic  dioxide,  and  ammonia,  which  were  placed 
there  for  its  use,  and  which  have  been  made  to  serve 
as  its  nourishment  and  food.  It  is  the  special 
office  of  the  plants  to  elaborate  from  these  few 
mineral  substances,  and  a  small  amount  of  earthy- 
salts,  all  the  materials  of  organized  beings.  The 
animal  receives  these  crude  materials  already  pre- 
pared, and  builds  with  them  its  various  tissues;  but 
no  sooner  are  the  cell-walls  finished,  and  the  struc- 
ture ready  to  discharge  its  vital  functions,  than  it  is 
consumed  by  almost  the  very  act  which  gave  it  life. 
The  carbonic  dioxide,  water,  and  ammonia  are  re- 
stored to  the  atmosphere,  and  the  cycle  is  complete. 
Of  this  Divine  economy  the  sun's  rays  are  the 
great  moving  cause,  and  it  is  their  mysterious  power 
which  is  constantly  reappearing  in  all  the  varied 
phases  of  organic  life.  And  not  in  these  alone  ;  for, 
as  we  have  seen,  this  same  gentle  influence  keeps  in 
motion  the  aerial  currents  which  blow  our  ships 
across  the  ocean.  It  raises  the  water  which  turns 
the  wheels  of  our  factories.  It  drives  the  locomotive 
over  the  iron  road,  and  impels  the  steamer  through 
the  waves.  It  roars  at  the  cannon's  mouth,  and 
charges  the  grander  artillery  of  the  skies.  There  is 
no  motion  on  the  globe  which  cannot  be  traced 
directly  or  indirectly  to  the  sun,  and  were  his  rays 
to  lose  their  mysterious  power,  all  nature  would  be- 
come silent,  motionless,  and  dead. 


228  THE  FIRST   CAUSE. 

But  in  thus  tracing  to  the  sun  all  these  varied 
phenomena,  let  us  not  forget  that  we  have  not  yet 
found  the  great  First  Cause.  The  problem  is  not 
yet  solved ;  the  profoundest  truth  has  yet  to  be 
told.  This  mysterious  force,  which  the  sun  pours 
in  ceaseless  floods  upon  the  earth, — whence  comes 
it  ?  You  have  already  answered  the  question.  The 
answer  is  on  your  lips.  I  have  but  to  re-echo  it,  and 
how  can  I  better  do  this  than  in  the  words  of  that 
blind  poet  to  whom  misfortune  had  revealed  the  true 
meaning  of  light : 

*'  Hail,  holy  Light !  offspring  of  Heaven  first  born ; 
Or  of  the  Eternal  co-eternal  beam 
May  I  express  thee  unblamed  ?  since  God  is  light, 
And  never  but  in  unapproached  light 
Dwelt  from  eternity,  dv^elt  then  in  thee, 
Bright  effluence  of  bright  essence  increate." 


CHAPTER  VIII. 

ARGUMENT   FROM   SPECIAL   ADAPTATIONS. 

I  HAVE  endeavored  thus  far  in  this  course  of  lec- 
tures to  present  a  few  of  the  prominent  illustrations 
of  the  attributes  of  God,  which  have  been  discov- 
ered in  the  adaptations  of  the  atmosphere  to  the 
conditions  of  organic  life  on  the  earth.  We  have 
read  together  one  brief  chapter  of  that  evidence  of 
design  with  which  the  book  of  nature  is  filled,  and 
I  cannot  but  trust  that  we  have  gained  from  our 
study  nobler  conceptions  and  more  enlarged  views 
of  the  wisdom,  power,  and  goodness  of  our  Heav- 
enly Father.  Every  one  who  accepts  the  Bible  as 
a  divine  revelation  will  rejoice  to  find  how  beauti- 
fully and  how  entirely  the  facts  of  science  confirm 
its  great  fundamental  truths.  But  have  not  these 
evidences  of  nature  a  greater  value  even  than  this  ? 
Do  they  not  prove,  independently  of  all  revelation, 
the  existence  of  a  wise  and  omnipotent  First  Cause, 
at  least  so  far  as  there  is  any  moral  certainty  in  the 
world  ?  I  am  persuaded  that  they  do,  and  I  believe 
that  they  furnish  the  only  logical  ground  on  which 
a  system  of  revealed  religion  can  be  based.  In  my 
introductory  lecture   I  stated  that    I  preferred  to 

22g 


230  CHARACTER   OF  THE  ARGUMENT. 

discuss  the  adaptations  of  nature  as  illustrations  of 
the  attributes  of  God,  rather  than  as  absolute  proofs 
of  His  being;  but  now  that  we  have  surveyed  the 
ground,  let  us  consider  whether  they  are  not  really 
moral  proofs,  with  all  the  certainty  that  any  proof 
not  strictly  a  mathematical  demonstration  can  give. 
The  argument  from  adaptation  is  one  which  ad- 
dresses itself  to  every  human  being.  It  is  suited  to 
every  intellect,  and  comes  home  to  every  man's  ex- 
perience. It  is  based  on  a  principle  of  the  human 
mind, — whether  the  result  of  experience  or  of  intu- 
ition we  need  not  inquire, — which  compels  it  to  infer 
design  when  it  sees  adaptation.  Who  doubts  that 
the  flint  arrow-heads  and  stone  implements  found 
in  New  England,  rough  and  misshapen  as  they  are, 
were  made  by  men  ?  To  question  the  universal 
belief  would  be  regarded  as  little  short  of  insanity. 
Why  then  not  apply  the  same  common  sense  to  the 
interpretation  of  nature  ?  The  unlettered  do,  and 
believe,  in  their  simple  faith,  that  the  feathered 
songster  and  the  delicate  flower  were  made  by  their 
Heavenly  Father's  hand.  It  is  only  those  of  us 
whose  minds  have  been  unsettled  by  the  subtilties 
of  logic  who  doubt,  and,  if  we  could  analyze  our 
doubts,  I  think  they  would  be  found,  in  most  cases, 
to  arise  from  a  vague  fear  that,  since  nature  stands 
on  a  level  so  much  above  man's  experience,  the 
ordinary  principles  of  reasoning  may  possibly  not 
apply,  and  we  may  be  misled  by  apparent  analogies. 
But  why  this  fear?  There  is  no  essential  difference 
between  the  adaptations  found  in  nature  and  the 
adaptations  made  by  men.     Both  employ  means  to 


CHARACTER  OF  THE  ARGUMENT.      23 1 

attain  some  important  result,  and  in  many  cases 
they  secure  the  end  by  precisely  the  same  means. 
The  telescope  and  microscope  are  but  reproductions 
of  the  eye,  and  imitate  in  all  their  essential  features 
this  beautiful  optical  apparatus  of  nature."^  It  is 
true  that  the  adaptations  of  nature  are  vastly  supe- 
rior to  the  results  of  human  skill,  and  it  is  also  true 
that  their  origin  is  beyond  our  personal  experience. 
We  have  seen  the  process  of  making  a  watch  and  the 
process  of  making  a  telescope.  We  know  how  the 
principles  of  both  were  discovered,  and  the  whole 
subject  lies  within  the  range  of  our  experience  ;  but 
no  man  ever  made  or  ever  can  make  an  eye,  and  the 
whole  process  of  its  growth  and  development  is  ut- 
terly beyond  the  range  even  of  man's  conception. 
All  this  is  true  ;  but  if  you  reflect  a  moment,  you  will 
find  that  this  is  just  what  is  to  be  expected,  seeing 
that  God  is  the  Creator  and  we  are  His  creatures, 
and  so  far  from  weakening,  this  very  characteristic 
greatly  strengthens  the  evidence.  Moreover,  it  must 
be  remembered  that,  if  the  design  is  of  an  infinitely 


*  The  power  which  the  eye  possesses  of  adaptation  to  near  and  dis- 
tant objects,  combining  the  uses  of  the  microscope  and  the  telescope, 
and  the  capacity  of  self-adjustment,  preserving  always  a  perfect  achro- 
matism and  freedom  from  spherical  aberration,  have  never  been 
reached  in  nearly  the  same  degree  by  art.  Moreover,  in  the  eye  this 
perfection  is  attained  with  a  focal  length  of  only  half  an  inch,  which 
vastly  increases  the  difficulty.  It  is  also  a  fact  worthy  of  notice,  that 
the  improvements  in  optical  instruments  have  preceded  rather  than 
followed  the  discoveries  of  physiologists,  thus  serving  to  explain  the 
functions  of  the  eye  ;  and  inventions  like  that  of  achromatic  lenses,  to 
which  men  have  been  led  by  theoretical  study,  have  been  found  to  be 
anticipated  in  nature. 


232  THE  ARGUMENT  CUMULATIVE. 

higher  order,  the  evidence  of  the  design  is  infinitely 
more  ample.  A  rude,  misshapen  image  is  a  con- 
vincing evidence  of  human  intelligence ;  but  all 
nature,  with  its  numberless  adaptations — from  the 
properties  of  the  crude  elements  up  to  the  wonder- 
ful structure  of  the  human  frame — is  given  us  as 
evidence  of  the  wisdom  of  God. 

The  argument  from  the  adaptations  of  nature  is 
of  the  kind  we  call  cumulative.  Its  force  depends 
on  the  concurrence  of  many  and  varied  examples. 
It  is  not  based  on  one  isolated  case  of  adaptation, 
or  even  on  a  thousand  ;  but  there  is  a  host  of  con- 
ditions, which  no  man  can  number,  each  adjusted  to 
each,  and  all  bound  together  in  one  harmonious 
whole.  Consider  only  the  examples  we  have  dis- 
covered in  the  very  narrow  field  to  which  we  have 
limited  our  study.  How  numberless  are  the  condi- 
tions on  which  the  harmonious  working  of  the  varied 
functions  of  the  atmosphere  depends  !  In  the  first 
place,  there  is  the  expansive  tendency  of  the  air, 
sustained  by  the  solar  heat,  and  restrained  by  the 
force  of  gravity,  by  which  alone  it  is  held  to  the 
surface  of  the  globe.  Then  there  is  the  density, 
exactly  adjusted  to  the  human  organism,  and  depend- 
ing on  the  measures  and  weights  of  the  solar  system. 
Next  there  are  all  the  delicate  relations  to  light, 
heat,  and  electricity.  Passing  to  the  separate  con- 
stituents of  the  atmosphere,  there  is  oxygen,  with 
its  three  distinct  modifications,  endowed  with  fiery 
afifinities,  and  yet  so  carefully  guarded  as  to  be  a 
beneficent  servant  of  man,  intrusted  with  most  varied 
and  seemingly  incompatible  functions,  and  discharg- 


FACTS    REVIEWED.  233 

ing  each  with  equal  fideHty  and  precision  ;  next, 
there  is  water,  nourishing  all  nature  with  its  dews 
and  rains,  tempering  the  polar  climates  with  the 
latent  warmth  of  its  genial  currents,  and  protecting 
with  its  great  frost-blanket  the  delicate  plants  from 
the  winter's  cold, — exceptional  in  all  its  qualities, 
and  each  adapted  to  some  beneficent  end  ;  then 
comes  carbonic  dioxide,  concealing  in  its  transparent 
folds  the  solid  framework  of  all  organized  beings, 
and  the  source  of  those  priceless  beds  of  coal,  with 
their  inexhaustible  stores  of  heat  and  force ;  and 
lastly,  but  not  least  in  interest  or  importance,  there 
is  nitrogen,  so  remarkably  inert,  and  yet  endowed 
with  such  varied  affinities,  forming  such  numberless 
compounds,  and  imparting  to  all  such  singular  in- 
stability. As  we  thus  hastily  review  the  ground  we 
have  surveyed  together,  you  will  recall  the  numer- 
ous adaptations  we  discovered  while  studying  the 
wonderful  cycles  of  change  in  which  all  these  sub- 
stances conspire,  wheel  revolving  within  wheel,  and 
yet  all  moving  with  such  delicacy  and  beauty  of  ad- 
justment that  no  jar  is  felt  through  all  this  compli- 
cated mechanism,  and  not  the  slightest  derangement 
occurs  in  any  of  its  ten  thousand  parts. 

Now  the  argument  for  design  unfolded  in  this 
brief  chapter  of  the  book  of  nature  comes  home  to 
us  with  the  cumulative  weight  of  all  this  testimony. 
Perhaps  plausible  objections  might  be  urged  against 
individual  examples  of  adaptation  which  have  been 
advanced  ;  but  any  one  who  questions  the  general 
fact  must  be  prepared  to  disprove  all.  Were  there 
but  a  single  instance  of  adaptation,  or  only  two  or 


234  THE  ARGUMENT   SUMMED   UP. 

three,  the  sceptic  might  urge  with  a  show  of  reason 
that  this  was  the  result  of  accident, — arose  from  the 
*'  fortuitous  concourse  of  atoms  "  ;  but  the  examples 
of  adaptations  which  we  have  discovered  merely  in 
the  atmosphere,  all  interlacing  with  each  other,  and 
all  working  together  in  the  general  scheme,  are  by 
themselves  alone  so  great  a  number  that,  if  we  take 
no  higher  ground  than  the  mathematical  theory  of 
probabilities,  the  chances  against  the  supposition 
that  this  system,  even  as  we  know  it,  was  the  result 
of  accident,  are  almost  infinite,  and  can  be  expressed 
numerically  only  when  the  sands  on  the  sea-shore 
are  counted.  If  such,  then,  is  the  weight  of  the 
evidence  which  the  atmosphere  gives,  what  must  be 
the  force  of  the  argument  in  which  all  nature  gives 
its  united  testimony?  Truly,  the  number  of  atoms 
in  the  universe  is  not  sufficiently  large  to  express 
the  probabilities  against  this  forlorn  hope  of  athe- 
ism ! 

But,  my  friends,  the  sceptic  should  be  heard,  and, 
having  presented  our  side,  let  us  listen  to  what  he 
has  to  say  in  reply.  The  whole  argument  from 
special  adaptations  may  be  summed  up  in  a  few 
words.  Within  the  sphere  of  human  experience, 
adaptation  proves  the  existence  of  an  intelligence 
adequate  to  the  conception  and  execution  of  the 
design.  We  find  in  nature  adaptations  similar  to  the 
results  of  human  intelligence,  only  of  an  infinitely 
higher  order,  and  hence  by  analogy  we  conclude 
that  these  must  have  issued  from  an  infinitely  wise 
and  omnipotent  Designer.  The  argument  assumes 
the  reality  of  the  human  intelligence  as  consciously 


BURDEN  OF  PROOF.  235 

a  power  and  an  originator  within  its  own  sphere,  and 
reasons  from  this  to  a  similar  conscious  intelhgence 
in  the  Author  of  nature.  The  argument  assumes, 
also,  the  truthfulness  of  the  human  faculties  as  a 
source  of  knowledge,  without  which  it  is  of  course 
useless  to  reason  at  all. 

Now  the  adaptions  of  nature  are  facts  which  every- 
one must  admit,  the  sceptic  among  the  rest.  More- ' 
over,  he  must  also  admit  that  the  conclusion  which 
we  have  drawn  from  these  premises  is  the  all  but 
universal  conclusion  of  mankind.  Plutarch,  writing 
eighteen  centuries  ago,  without  the  light  of  the 
Christian  revelation,  bears  this  remarkable  testi- 
mony to  the  universality  of  the  religious  idea:  **If 
you  go  through  the  world,  you  may  find  cities  with- 
out walls,  without  letters,  without  rulers,  without 
dwellings,  without  wealth,  without  money,  without 
theatres  and  manly  sports  ;  but  there  was  never  yet 
seen,  nor  shall  be  seen,  by  man  a  single  city  without 
temples  and  gods,  or  without  prayers,  oaths,  proph- 
ecies, and  sacrifices,  used  to  obtain  blessings  and 
benefits,  or  to  avert  curses  and  calamities.  Nay,  I 
am  of  opinion  that  a  city  might  be  sooner  built 
without  any  ground  beneath  it,  than  a  common- 
wealth could  be  constituted  altogether  destitute  of 
belief  in  the  gods,  or,  being  constituted,  could  be 
preserved.*'  *     The  discoveries  of  modern  travellers 

■^  Evftoi'^  6^  ay  kitiwv  TtoXei^  dretxidrov^f  dypaj.i).idTov<^, 
d/JadiXevTov<5,  domovS,  dxf^r/udrovS,  vof.n6uaTo<i  uij  dsojue- 
ra'5,  dTtei'fjovS  OedrpGov  xai  yvjuvadiGDV  dvtspov  Ss  TtoXsaoi 
nai  dOeov,  jtii)  XP^M^'^V'^  tvxctl?,  juj^de  opHoi<^,  jtcf^de  tuayreiaii, 
jLir/de  Ovdi'aiS  kii^   dya^oi^,  juf/d^   dnorpoitali  HaKcoy,  ovdei<5 


236  PLUTARCH'S    STATEMENT. 

have  not  more  fully  confirmed  the  general  truth  of 
Plutarch's  statement,  than  the  experiments  of  mod- 
ern socialists  have  proved  the  soundness  of  his 
opinion.  No  savage  tribe  has  yet  been  found  on 
which  a  belief  in  a  higher  power  has  not  at  least 
glimmered,  and  no  community  which  has  attempted 
to  ignore  religion  has  lasted  a  century.  The  scep- 
tic, then,  if  he  rejects  our  conclusion,  is  bound 
to  prove  that  the  natural  inference  of  man  is  based 
in  error.  If  he  sets  aside  the  general  rule  of  faith, 
and  refuses  assent  to  the  universal  creed, — "  Quod 
semper,  quod  ubique,  quod  ab  omnibus  creditum 
est,*'"^ — he  must  explain,  whatever  theory  he  may 
adopt,  how  it  comes  to  pass  that  all  mankind  have 
been  duped,  and  all  nature  has  issued  in  a  lie.  The 
burden  of  proof  is  with  him,  and  how  does  he  meet 
it  ?     Generally  in  one  of  two  ways. 

In  the  first  place,  he  attacks  the  validity  of  the 
conclusion  on  purely  speculative  grounds,  saying 
that  adaptation  is  no  longer  an  evidence  of  design 
when  applied  to  subjects  beyond  the  range  of  all 
human  experience.  He  may  urge,  and  urge  with 
reason,  that  in  nature  we  have  no  sure  criterion  by 
which  we  can  distinguish  between  means  and  ends, 
between  what  is  cause  and  what  is  effect.  He  may 
support  this  position  by  questioning,  with  Hume, 
the  competency  of  the  human  faculties  as  a  source 

Idriv  ov8^  edrax  ysyovcbi  Bearjj'i'  dXXd  7t6Xi<^  ar  JlLoi  8okeX 
l^idXXor  lddq)OV^  X^P^^f  V  TtoXirela  TTJi  Ttepi  OecSv  do^r^S  vq)ai- 
pEf)8i6r/<^  7tarrd7ta6i,  6vdra6ir  XafSelv,  rf  Xa/Jovda  rr/prjdai, 
Plutarch,  Upo?  KoXg6t?/v,  xxxi. 

*  Vincentius  Lerinensis,  written  434  A.  D. 


^^     ^/ 


DEMONSTRATION   NOT   CLAIMED.  237 

of  knowledge,  or,  like  Comte,  he  may  deny  all  knowl- 
edge of  final  causes,  and  maintain  that  there  is  no  \ 
evidence  of  anything  behind  the  external  phenomena 
of  nature;  but  whatever  form  the  scepticism  may 
assume,  the  conclusion  is  the  same,  and  the  argu- 
ment for  design  is  ruled  out  as  invalid. 

With  regard  to  this  position  I  have  only  a  few 
words  to  say.  Design  in  nature,  I  admit,  cannot  be 
demonstrated ;  for  the  truths  of  natural  religion  can- 
not be  evolved  from  a  mathematical  formula.  The 
argument  is  based  on  analogy,  and  although  the 
analogies  are  so  close  and  so  broad  that,  to  my  mind, 
they  amount  to  moral  proofs,  and  the  conclusion 
appears  as  certain  as  any  theorem  of  geometry,  still 
I  admit  that  the  evidence  is  probable,  and  not 
demonstrative.  But  as  a  student  of  physical  science 
it  is  not  my  business  to  defend  the  credibility  of  the 
human  faculties,  or  to  discuss  the  doctrine  of  causa- 
tion. The  task  belongs  to  the  metaphysicians,  and, 
as  I  stated  in  my  first  lecture,  I  shall  not  encroach 
on  their  peculiar  province.  Nor  do  I  think  it  im- 
portant to  dwell  on  the  value  of  analogical  reason- 
ing. Modern  writers  have  not  been  able  to  add 
much  to  Bishop  Butler's  masterly  discussion  of  the 
subject,  and  every  man,  however  sceptical  he  may 
be  in  his  speculative  opinions,  must  admit,  with  the 
author  of  "  The  Analogy,"  that  "  probability  is  the 
very  guide  of  life."  One  consideration,  however, 
may  be  of  value  in  answering  objections,  namely, 
that  since  the  difficulties  which  are  found  in  natural 
theology  reappear  with  equal  strength  in  all  depart- 
ments of  knowledge,  no  objections  can  be  reason- 


238  PROVINCE   OF  DEMONSTRATION. 

ably  urged  against  the  methods  of  the  former,  which 
do  not  apply  equally  well  to  our  most  familiar  pro- 
cesses of  thought.  It  may  be  fairly  presumed  that 
such  objections  are  more  apparent  than  real,  and  that 
they  indicate  not  the  inconsequence  of  our  logic, 
but  only  the  necessary  limitations  of  our  faculties. 

Now  analogy  is  not  only  the  guide  of  common 
life,  but  it  is  also  the  basis  on  which  physical 
science  chiefly  rests ;  and  if  this  method  of  reason- 
ing be  disallowed,  all  the  results  of  science  beyond 
those  of  mere  observation  and  demonstration  must 
fall  with  it.  It  is  frequently  said,  that  scientific 
truth  can  be  demonstrated,  but  religious  truth  must 
be  accepted  on  faith ;  and  in  part  this  is  true ;  but 
the  statement  is  one  of  those  loose  sayings  whose 
partial  truth  only  renders  the  latent  error  more 
dangerous.  No  word  is  more  frequently  misused 
than  "demonstration."  Technically,  this  term  only 
applies  to  that  form  of  absolute  proof  with  which  we 
deal  in  geometry  or  pure  logic ;  but,  popularly,  a 
principle  is  said  to  be  demonstrated  when  all  that 
can  be  claimed  for  it  is  a  high  degree  of  moral 
certainty.  In  this  double  use  of  the  term  the  error 
of  the  above  statement  lies,  for  it  is  made  in  one 
sense,  and — frequently  at  least — understood  in  the 
other.  Truth  wholly  new  is  never  reached  by  the 
methods  of  demonstration ;  for  demonstration  can- 
not yield  what  is  not  already  implied  in  the  premises 
with  which  it  starts.  The  truths  of  geometry  and 
mechanics  may  be  demonstrated  ;  but  then  they  are 
virtually  contained  in  the  axioms  and  definitions  on 
which  these  sciences  rest.     All  scientific  generaliza- 


ANALOGY   THE   CHIEF   GUIDE.  239 

tion  is  based  on  analogy ;  and  moreover,  a  great 
mass  of  the  scientific  truth  which  lies  within  the 
range  of  direct  observation  we  owe  to  the  same 
principle ;  for  even  here  analogy  directed  the  stu- 
dent to  what  he  subsequently  observed. 

Indeed,  the  great  inspiring  and  directing  power 
in  the  minds  of  the  successful  investigators  of  nature 
is  the  force  of  analogy.  It  is  this  which  constantly 
leads  them  to  pronounce  conclusions  unsound,  al- 
though apparently  sustained  by  experiment,  and  to 
accept  others  which  are  seemingly  at  variance  with 
facts.  It  is  this  which  leads  them  through  long  and 
laborious  investigations  to  establish  principles  which 
they  believe  to  be  true,  and  sustains  them  in  their 
efforts  through  successive  failures  to  ultimate  suc- 
cess. As  indefinite  and  uncertain  as  the  analogies 
of  nature  frequently  seem  to  be,  as  unsatisfactory  as 
they  may  appear  to  the  great  mass  of  mankind,  and 
as  impossible  as  it  is  to  make  them  intelligible  ex- 
cept to  those  already  versed  in  scientific  inquiries, 
yet  the  history  of  science  shows  that,  when  based 
on  an  extended  knowledge  and  a  mature  experience, 
they  very  seldom  lead  astray. 

The  method  of  scientific  discovery  is  frequently 
misunderstood,  and  the  philosophy  of  Bacon,  how- 
ever important  in  correcting  old  abuses,  has  done 
not  a  little  towards  creating  the  misapprehension. 
Many  persons  seem  to  think  that  the  author  of 
the  Novum  Organum  gave  to  man  a  rule,  by  which, 
with  the  aid  of  a  sort  of  mechanical  logic  called 
induction,  the  laws  of  nature  may  be  discovered 
very  much  as  a  last  is  turned  out  by  a  lathe.     Yet 


240         METHOD   OF  SCIENTIFIC   DISCOVERY. 

nothing  could  be  further  from  the  truth.  So  far  as 
the  observation  of  phenomena  is  concerned, — which 
must  always  be  the  occupation  of  the  great  mass  of 
scientific  men, — the  methods  are  as  mechanical  as 
those  of  other  learned  professions,  requiring  chiefly 
a  quick  eye,  a  delicate  touch,  a  ready  perception, 
and,  most  of  all,  a  clear  head  capable  of  discriminat- 
ing between  the  accidentals  and  the  essentials,  which 
are  always  singularly  blended  in  natural  phenomena. 
But  the  great  generalizations,  which  form  the  frame- 
work of  knowledge,  are  not  reached  by  rule ;  nor,  as 
a  general  thing,  are  they  in  their  inception  of  slow 
growth.  On  the  contrary,  they  usually  come  like 
intuitions  to  the  mind,  with  the  rapidity  of  the 
lightning's  flash,  and  it  is  frequently  possible  to 
mark  the  day  and  the  hour  when  the  revelation  was 
made.  But  such  revelations  of  scientific  truth  are 
vouchsafed  only  to  those  highly  favored  minds  which 
through  long  study  and  patient  investigation  have 
been  brought  into  perfect  sympathy  with  the  har- 
monies of  nature ;  and  if  we  analyze  the  conditions 
of  the  mental  process,  we  shall  find  that  these  great 
discoveries  are  really  the  result  of  analogical  rea- 
soning. 

But  although  the  conception  is  thus  sudden,  the 
verification  of  the  truth  is  frequently  long  and  labo- 
rious. Great  discoveries  are  not  achieved  in  an  hour 
or  a  day.  Nature  has  so  concealed  her  truths,  and 
surrounded  them  by  so  many  adventitious  circum- 
stances, that  they  can  be  disclosed  to  the  world  only 
after  long  and  careful  study.  First  comes  the  con- 
ception, afterwards   the   toilsome  investigation  by 


METHOD   OF  SCIENTIFIC  DISCOVERY.  24I 

which  it  is  proved  that  the  facts  of  nature  accord 
with  the  generalization.  The  investigation  may 
lead  to  a  great  modification  of  the  original  idea,  or 
may  show  that  it  must  be  wholly  abandoned,  and 
meanwhile  another  may  have  taken  its  place,  to  go 
through  the  same  scrutiny  in  its  turn  ;  but  still  the 
conception  which  proves  to  be  the  law  of  nature  is 
the  real  discovery.  This,  as  we  have  seen,  is  the  re- 
sult of  analogy,  and  most  clearly  vindicates  the  re- 
lationship of  the  mind  of  man  to  the  Intelligence 
whence  issued  the  universe. 

Every  great  scientific  generalization  will  illustrate 
more  or  less  clearly  the  principles  here  stated.  It 
is  true  that  many  minds  frequently  concur  in  de- 
veloping one  grand  idea,  and  the  evolution  may  oc- 
cupy so  long  an  interval  of  time  that  the  new  truth 
appears  to  be  the  growth  of  an  age,  rather  than  the 
gift  of  any  one  man.  Yet  it  is  possible  in  almost 
every  case  to  trace  the  successive  steps  of  the  dis- 
covery. This  is  especially  true  of  the  law  of  gravi- 
tation. Whether  the  first  idea  was  suggested  to 
Newton  by  the  fall  of  an  apple,  it  is  not  important 
to  inquire;  but  the  popular  anecdote  illustrates  the 
nature  of  the  original  thought,  which  was  undoubt- 
edly sudden  and  intuitive,  although,  as  Newton  has 
himself  expressly  stated,  it  was  the  result  of  ana- 
logical reasoning.  The  conception  once  formed,  the 
work  of  verification  was  long  and  laborious,  and  the 
results  were  at  first  so  unsatisfactory  that  Newton  at 
one  time  abandoned  his  theory  altogether,  as  un- 
supported by  observation.  It  was  not,  indeed,  un- 
til a  new  arc  of  the  meridian  had  been  measured  by 


242  METHOD   OF  NATURAL  RELIGION. 

Picard  in  France — several  years  after  the  first  con- 
ception— that  the  facts  were  found  to  agree  even 
approximately  with  the  theory,  and  astronomers  have 
been  occupied  ever  since  in  verifying  the  grand 
thought.  The  same  general  facts  reappear  in  the 
case  of  the  wave-theory  of  light,  first  conceived  by 
Huyghens  and  subsequently  verified  by  the  succes- 
sive discoveries  of  Malus,  Fresnel,  and  Young  ;  and 
we  may  lay  it  down  as  an  almost  universal  principle, 
that  scientific  truth  is  discovered  through  analogy 
and  verified  by  comparison  with  the  facts  of  nature. 

If  now  you  will  turn  to  the  great  central  truth  of 
natural  religion,  you  will  find  that  it  has  as  ^ood 
credentials  as  the  best  established  laws  of  science. 
We  have  first  the  conception, — not  only  the  concep- 
tion of  a  few  highly  gifted  minds,  but  the  universal 
conception  of  mankind.  We  find  afterwards  this 
conception  verified, — not  only  in  the  history  of  the 
race,  but  also  in  the  experience  of  each  individual 
man,  and  moreover,  the  conception  is  apparently  in- 
tuitive in  every  mind.  Even  if  the  sceptic  denies 
the  reality  of  both  special  and  general  providence, 
he  must  admit  that,  as  the  most  universal  rule,  both 
history  and  experience  have  only  served  to  confirm 
and  strengthen  the  religious  idea. 

We  now  return  to  the  remark  above  quoted,  bet- 
ter able  both  to  appreciate  the  truth  it  contains  and 
to  unmask  the  fallacy  it  conceals.  A  large  part  of 
the  results  of  science  may  be  demonstrated,  but 
only  such  truths  as  are  already  contained  in  the 
premises  on  which  the  demonstration  rests  are  capa- 
ble of  this  absolute  proof ;  and  these  are  in  all  cases 


PROVINCE   OF  FAITH.  243 

reached  by  the  human  intelligence  working  on  its 
own  definitions  and  processes  of  thought,  and  this, 
too,  even  when  the  theoretical  truth  is  afterwards 
found  realized  in  nature.  The  highest  forms  of  sci- 
entific truth  are  not  capable  of  demonstration,  and 
rest  only  on  probable  evidence,  although  the  prob- 
ability in  their  favor  may  be  so  great  as  to  beget 
the  highest  degree  of  moral  certainty.  In  like  man- 
ner, a  great  part  of  the  truths  of  religion  must  be  ac- 
cepted on  faith ;  but  then  the  evidence  in  favor  of 
the  great  fundamental  truth  of  natural  religion  is 
as  strong  as  the  evidence  for  any  theory  of  science, 
and  the  certainty  is  as  great.  Moreover,  faith  is  not 
peculiar  to  religion.  All  our  knowledge  not  the 
resuir^STp^Fsonal  observation  and  investigation  is 
held  on  faith,  that  is,  on  trust  in  other  men,  and 
absolutely  all  knowledge  is  held  on  trust  in  the 
authority  of  our  own  mental  powers.  Much  of  the 
knowledge  which  we  hold  without  question,  it  is 
utterly  beyond  the  capacity  of  our  own  intellects  to 
verify,  and  moreover,  no  one  doubts  the  existence  of 
truths  which  now  lie  beyond  the  scope  of  the  most 
gifted  genius,  but  which  hereafter  may  be  attained 
by  man.  The  scientific  truths  which  it  is  not  essen- 
tial for  us  to  know  are  left  in  the  dark  on  purpose 
to  stimulate  study,  and  thus  to  educate  the  human 
race.  Religious  truths,  on  the  other  hand,  it  is  es- 
sential for  us  to  know,  and,  since  they  in  like  manner 
transcend  our  present  powers,  they  have  been  spe- 
cially revealed.  We  are  called  upon  to  accept  them 
on  sufficient  evidence,  and  this  is  all  that  is  meant 
by  faith.     Faith,  then,  is  as  truly  a  ground  of  belief 


244  REPLY   TO   THE   SCEPTIC. 

in  science  and  in  common  life  as  it  is  in  religion, 
and  it  occupies  a  more  important  place  in  religion 
only  because  religious  truth  is  itself  so  important, 
and  so  greatly  transcends,  in  its  essence,  our  limited 
human  faculties. 

Our  reply,  then,  to  the  first  position  of  the  sceptic 
is  this.  Your  objections  apply  as  well  to  all  knowl- 
edge as  they  do  to  religious  truth,  and,  if  you  are 
consistent  with  yourself,  you  must  reject  the  evi- 
dences of  science  as  well  as  the  evidences  of  religion."^ 
As  we  are  not  prepared  to  go  this  length,  we  shall 
with  equal  consistency  hold  to  both.  It  is  but  jus- 
tice to  state  that  Hume,  the  most  philosophical  of 
the  sceptics,  pushed  his  speculations  to  their  neces- 
sary consequences,  and  denied  the  existence  of 
matter  and  spirit  alike.  But  although  from  its  very 
boldness  difficult  to  refute,  this  form  of  scepticism 
is  by  no  means  the  most  dangerous;  for  in  the 
present  age  of  the  world  a  system  of  philosophy  is 
not  likely  to  gain  many  adherents  which,  in  the 
first  article  of  its  creed,  utterly  shocks  all  human 
self-conceit  by  declaring  that  man  neither  knows 
nor  can  know  anything  with  certainty. 

In  the  second  place,  the  sceptic  attacks  the  argu- 
ment for  design  by  setting  up  a  theory  of  his  own 
to  explain  the  origin  of  the  universe.  He  tacitly 
admits  that  the  burden  of  proof  is  with  him,  and 
that,  if  he  rejects  the  popular  belief,  he  is  bound  to 
show  how  this  cosmos  might  have  been  issued  with- 


*  See  this  point  well  reasoned  in  Balfour's  Defe7tce  of  Philosophic 
Doubt 


ABSOLUTE   MATERIALISM.  245 

out  intelligence  and  without  a  God.  This  he  at- 
tempts to  do,  and  the  result  is  nearly  as  many  the- 
ories as  there  have  been  strong  scientific  intellects 
in  the  world  united  with  unbelieving  hearts.'  To 
refute  each  of  these  theories  in  detail  would  be  a 
labor  like  that  of  Hercules  in  slaying  the  Lernaean 
Hydra ;  for  until  Almighty  Power  shall  sear  the  foul 
sore  from  which  the  whole  brood  proceeds,  their 
unholy  heads  will  start  up  more  rapidly  than  they 
can  be  cut  down.  The  most  daring  theories  of  this 
kind  are  those  of  the  German  materialists  of  the 
present  day.  As  much  as  they  may  differ  among 
themselves  in  regard  to  details,  the  boldest  of  these 
speculators  agree  in  maintaining  that  absolutely 
nothing  exists,  or  ever  has  existed,  except  matter 
and  motion ;  that  matter  in  its  essence  is  uncreated 
and  eternal ;  that  motion  is  self-sustained  ;  that  mind 
is  only  a  mode  of  motion,  and  that  all  the  phenom- 
ena both  of  matter  and  of  mind  are  the  working 
out  of  an  inexorable  necessity.  Hence  they  con- 
clude that  religion  is  a  fable,  and  immortality  a 
dream. 

Here  is  atheism.  This  is  the  natural  fruit  of 
materialism  ;  and  we  are  glad  that  it  has  ripened, 
that  men  may  see  how  disgusting  and  revolting  it  is, 
and  how  corrupt  the  tree  must  be  which  can  bear 
such  fruit.  We  are  glad  that  men  should  know 
what  must  be  the  result  of  all  their  vain  speculation 
and  the  seeking  after  false  gods.  The  theory  is 
perfectly  consistent  with  itself,  and  an  absolute 
necessity  if  nature  be  divorced  from  its  Creator ; 
for  all  philosophy  has  proved  that  either  the  the- 


246  ABSOLUTE  MATERIALISM. 

ory  of  the  Christian,  or  this  theory  of  the  materi- 
ahst,  with  all  its  enormity,  must  be  true.  There  is 
no  half-way  halting-place  between.  This  course  of 
lectures  has  been  a  continued  protest  against  the 
materialist's  interpretation  of  nature,  and  I  have 
not  another  word  to  add ;  for  if  a  man  wishes  to 
believe  that  his  purest  loves  and  his  holiest  affec- 
tions are  only  motions  of  brain-particles,  nothing 
that  can  be  said  would  have  the  slightest  weight. 
If  he  has  not  already  the  refutation  in  his  own  con- 
sciousness of  being,  human  power  cannot  aid  him  ; 
no  philosophy  can  extricate  him  from  the  slough. 
*'  Ephraim  is  joined  to  idols  ;  let  him  alone." 

It  is  seldom,  however,  that  materialism  shows  its 
revolting  features  among  us.  It  is  too  cunning  and 
too  cautious.  It  always  appears  disguised,  and  is 
for  this  reason  far  more  seductive.  It  presents  the 
attraction  of  great  learning  and  of  great  apparent 
profundity,  entangling  many  in  its  meshes  before 
they  are  aware  of  their  danger.  It  does  not  deny 
the  reality  of  the  human  intellect,  but,  on  the  con- 
trary, takes  pride  in  its  authority  and  power.  It 
even  admits  the  evidence  of  design,  but  at  the  same 
time  insidiously  undermines  all  religious  belief ;  not 
so  much,  however,  by  what  it  declares,  as  by  what 
it  leaves  to  be  inferred ;  not  so  much  by  the  doc- 
trines it  inculcates,  as  by  the  spirit  it  keeps  alive 
and  fosters.  In  this  refined  form,  materialism  is  by 
far  the  most  prevalent  phase  of  the  unbelief  of  our 
time,  and  it  is  difficult  to  meet  chiefly  on  account  of 
its  very  vagueness  and  simulation.  It  lives  almost 
entirely  in  the  ever-changing  theories  and  specula- 


DEVELOPMENT  THEORIES.  247 

tions  of  science,  which  it  utterly  misinterprets  and 
misapplies,  forgetting  that  they  are  merely  pro- 
visional expedients,  which  the  next  wave  of  advanc- 
ing knowledge  may  wash  away.  Development  is  the 
pet  word  of  its  philosophy,  and  it  constantly  aims 
to  show  how  the  whole  scheme  of  nature,  with  all 
its  adaptations,  might  have  been  evolved  through 
the  concurrent  action  of  various  unintelligent  causes 
alone.  As  it  attacks  the  argument  for  design  on 
scientific  grounds,  it  becomes  the  duty  of  the  stu- 
dent of  nature  to  expose  its  errors.  It  is,  however, 
a  most  Protean  antagonist,  and  no  sooner  is  it  de- 
feated in  one  form  than  it  reappears  in  another. 
Every  new  development  theory  in  any  department 
of  science  furnishes  it  with  fresh  food.  For  a  long 
time  the  famous  nebular  hypothesis,  broached  in 
Laplace's  Systhne  du  Monde,  supplied  it  with  abun- 
dant nourishment ;  and  within  the  last  twenty  years 
it  has  taken  a  fresh  start,  and  grown  most  vigorously, 
on  Mr.  Darwin's  very  ingenious  book  entitled  The 
Origin  of  Species,  But  these  are  only  two  examples 
of  a  large  number  of  similar  works,  which,  being 
less  able  and  less  original,  have  had  their  day  and 
been  forgotten. 

The  danger  of  these  works  lies  not  so  much  in 
what  they  actually  contain,  as  in  their  general  ten- 
dency ;  not  so  much  in  the  theories  of  their  authors, 
as  in  the  wrong  conclusions  which  will  inevitably  be 
drawn  from  them,  and  to  which  in  many  cases  they 
logically  lead.  Darwin,  for  example,  professes  to 
show  that  all  the  living  forms  of  plants  and  animals, 
man  included,  have  been,  during  the  geological  ages, 


248  DUTY   OF  SCIENTIFIC   TEACHERS. 

slowly  developed  from  a  few  germs,  or  possibly  from 
only  one,  by  the  action  of  a  principle  which  he  calls 
the  *'  law  of  natural  selection,"  and  he  sustains  the 
hypothesis  by  a  most  formidable  array  of  experi- 
ments and  facts.  Such  a  theory  as  this,  ingenious 
if  not  true,  professing  to  explain  one  of  the  great- 
est mysteries,  and  presented  in  a  fascinating  style, 
finds  converts  everywhere,  and  this,  too,  on  grounds 
entirely  independent  of  its  scientific  merit.  That 
very  same  noble  aspiration  which  leads  men  to  im- 
peril even  life  itself  in  investigating  the  secrets  of 
nature,  makes  them  also  ready  to  lend  a  willing  ear 
to  any  theory  which  professes  to  explain  the  mystery 
of  creation.  Hence  the  reason  why  works  like  the 
Vestiges  of  Creation^  and  those  just  mentioned,  cap- 
tivate and  injure  so  many.  If  they  merely  stimu- 
lated curiosity,  and  led  to  study,  no  one  could  object 
to  their  influence,  however  erroneous  he  might  think 
their  philosophy.  But,  unfortunately,  most  readers, 
of  whom  it  is  no  disparagement  to  say  that  they  are 
not  in  a  condition  to  weigh  the  evidence,  accept  the 
theory  without  examination,  and,  if  sceptically  in- 
clined, their  whole  belief  in  an  overruling  Providence 
is  shaken  to  its  base. 

It  is  in  vain  to  urge  that  these  theories  may  be 
consistent  with  a  pure  faith  ;  for  as  long  as  they  are 
not  so  regarded  by  the  popular  mind, — which  invari- 
ably appeals  to  them  as  proofs  of  materialism, — the 
evil  which  they  cause  is  not  remedied.  It  may  be 
said,  and  said  with  some  justice,  that  a  writer  cannot 
be  blamed  for  the  abuse  of  his  theory ;  but  it  must 
be  admitted  that  the  abuse  is  a  great  evil,  and  an 


DESIGN  NOT  INVALIDATED.  249 

author,  if  he  be  a  rehgious  man,  is  bound  to  guard 
against  it  by  every  means  in  his  power.  We  should 
be  very  slow  to  charge  any  man  with  infidelity,  for 
we  know  how  often  the  human  mind,  in  its  eccen- 
tricities and  inconsistencies,  has  united  a  true  faith 
to  the  most  sceptical  and  subversive  speculations. 
But  we  do  say,  that  the  least  a  Christian  philosopher 
can  do  for  his  faith  is  to  give  such  a  tone  and  spirit 
to  his  work  as  to  render  misinterpretation  impos- 
sible;  and  if  he  neglects  to  do  this,  he  has  no  right 
to  complain  if  his  own  opinions  are  misjudged. 

I  shall  not  attempt  to  discuss  the  intrinsic  value 
of  the  various  theories  of  development,  but  leaving 
this  task  to  those  who  are  competent  judges,  let  us 
inquire  what  bearing  they  have  on  the  evidence  of  de- 
sign. I  answer,  absolutely  none.  Assuming  that  Mr. 
Darwin  could  establish  his  peculiar  theory  in  all  its 
generality, — and  I  have  no  doubt  that  it  has  a  large 
element  of  truth, — it  would  not  impair  the  evidence 
of  design  in  the  slightest  degree,  and  the  same  is 
true  of  any  development  theory  whatsoever,  short  of 
absolute  materialism.  Those  persons  who  imagine 
that  they  overthrow  natural  religion,  fall  into  a  capi- 
tal error.  It  requires  manifestly  the  same  infinite 
intelligence  to  creaTte  a  universe  by  a  process  of  de- 
velopment as  by  a  single  creative  fiat.  Your  belief 
that  the  beautiful  piece  of  mechanism  standing  on 
your  mantel-shelf  was  made  by  an  intelligent  man, 
would  not  be  impaired  if  you  were  told  that  the  ar- 
tist was  employed  several  years  in  its  construction. 
The  evidence  of  design  in  the  clock  is  in  its  beauti- 
fully adjusted  mechanism.     The  evidence  of  design 


250  A  LOGICAL  THEFT. 

in  nature  is  in  the  wonderful  adaptation  of  its  parts. 
We  can  easily  go  back  in  the  geological  records  to 
the  time  when  the  present  order  of  nature  did  not 
exist,  and  the  fact  that  the  innumerable  forms  of  or- 
ganic life,  with  the  adaptations  of  currents,  soil,  and 
climate  essential  to  their  being,  have  been  developed 
out  of  the  conditions  which  existed  on  the  globe 
during  the  coal  epoch,  is  no  less  an  evidence  of 
design  than  the  fact  that  the  clock  was  developed 
out  of  the  crude  iron  and  brass  used  in  its  con- 
struction. 

"We  lament,"  says  Dr.  Martineau,"^  "to  see  the 
question  between  a  sudden  and  a  gradual  genesis  of 
organic  types  discussed  on  both  sides — not,  indeed, 
by  the  principals  in  the  dispute,  but  by  secondary 
advocates — too  much  as  if  it  were  a  question  be- 
tween God  and  no  God.  In  not  a  few  of  the  pro- 
gressionists the  weak  illusion  is  unmistakable,  that 
with  time  enough  you  may  get  everything  out  of 
next  to  nothing.  Grant  us,  they  seem  to  say,  any 
tiniest  granule  of  power,  so  close  upon  zero  that  it 
is  not  worth  begrudging;  allow  it  some  trifling  ten- 
dency to  infinitesimal  increment ;  and  we  will  show 
you  how  this  little  stock  became  the  cosmos  with- 
out ever  taking  a  step  worth  thinking  of,  much  less 
constituting  a  case  for  design.  The  argument  is  a 
mere  appeal  to  an  incompetency  in  the  human 
imagination,  in  virtue  of  which  magnitudes  evading 
conception  are  treated  as  out  of  existence,  and  an 
aggregate  of  inappreciable  increments  is  simultane- 

*  Essays,  Nature  and  God. 


TOPSYS   ANSWER.  251 

ously  equated  in  its  cause  to  nothing,  in  its  effect  to 
the  whole  of  things.  You  manifestly  want  the  same 
causality,  whether  concentrated  on  a  moment  or 
distributed  through  incalculable  ages,  only,  in  draw- 
ing upon  it,  a  logical  theft  is  more  easily  committed 
piecemeal  than  wholesale.  Surely  it  is  a  mean  de- 
vice for  a  philosopher  thus  to  crib  causation  by  hair- 
breadths, to  put  it  out  at  compound  interest  through 
all  time,  and  then  disown  the  debt ;  and  it  is  in  vain, 
after  all ;  for  dilute  the  intensity  and  change  the 
form  as  you  will  of  the  Power  that  has  issued  the 
universe,  it  remains,  except  to  your  subjective  illu- 
sion, nothing  less  than  infinite,  and  nothing  lower 
than  divine.'* 

The  genesis  of  nature  has  been  unquestionably  a 
process  of  development.  But  let  us  not  be  frightened 
by  words.  Development  is  only  another  name  for 
growth,  and  it  obviously  brings  us  no  nearer  to  the 
final  cause  of  a  given  product  to  say  that  it  has  grown. 
Topsy  in  answering  her  catechist's  "  Do  you  know 
who  made  you  ?  '*  with  "  Nobody  as  I  knows  on — I 
spect  I  growed,"  was  fully  as  wise  and  far  more  hum- 
ble-minded than  those  philosophers  who  attempt  to 
cover  up  the  same  answer  under  high-sounding  tech- 
nical phraseology.  Growth  is  the  order  of  nature, 
but  even  in  its  simplest  phases  it  is  as  mysterious  a 
phenomenon  to-day  as  it  was  when  the  mind  of 
man  was  first  conscious  of  the  fact.  That  of  two  mi- 
nute eggs,  in  which  no  anatomist  can  discover  any 
structural  difference,  the  one  should  in  a  few  short 
years  develop  an  intelligence  like  Newton's,  while  the 
other  soon  ends  in  a  Guinea-pig,  is  certainly  as  great 


252  GENESIS   OF   SPECIES. 

a  mystery  as  that  in  the  course  of  unnumbered  ages 
monkeys  by  insensible  gradations  should  grow  into 
men.  The  growth  of  each  man  from  a  microscopic 
germ  is  not  understood  one  whit  more  fully  than  the 
genesis  of  a  species,  and  the  only  difference  is  that 
while  in  the  first  case  we  are  familiar  with  all  the  stages 
of  the  growth,  in  the  last  case  we  know  nothing  with 
certainty  except  the  final  result.  Surely  no  one 
really  imagines  that  the  first  man  came  "  full  armed, 
like  Minerva  from  the  brain  of  Jove.'*  There  must 
have  been  growth,  and  how  utterly  immaterial  it  is  to 
our  present  discussion  at  what  point  the  growth 
began.  Moreover,  how  evident  it  is  that  the  growth 
of  a  species  is  as  legitimate  an  object  of  scientific 
investigation  as  the  growth  of  an  individual;  and 
further,  that  if  we  were  as  familiar  with  the  successive 
stages  in  the  growth  of  a  species  as  we  are  with  those 
in  the  growth  of  each  individual  man,  we  should  be 
just  as  far  from  a  knowledge  of  the  efficient  causes 
in  the  first  case  as,  with  all  our  careful  observation 
and  study,  we  now  are  in  the  last  case.  But  although 
a  knowledge  of  the  efficient  causes  may  in  either 
case  be  beyond  the  reach  of  positive  science,  yet 
we  have  reason  to  expect  that  further  investigation 
will  lead  to  the  same  kind  of  knowledge  in  regard 
to  the  growth  of  a  species  that  we  now  have  in 
regard  to  the  growth  of  each  individual  animal  or 
plant. 

Again,  as  we  well  know,  growth  in  nature  is  very 
greatly  influenced  by  secondary  causes  of  various 
kinds,  such,  for  example,  as  soil  and  climate ;  and  as 
with  the  growth  of  the  individual,  so,  undoubtedly, 


DARWIN*S   THEORY.  253 

with  the  growth  of  the  species.  Moreover,  no  one  can 
doubt  the  potency  of  the  causes  which  have  been 
so  acutely  studied  by  Mr.  Darwin.  It  is  the  busi- 
ness of  science  to  study  these  secondary  causes, 
and  the  nature  and  extent  of  their  influence  are 
questions  of  fact  to  be  decided  by  scientific  investi- 
gation, and  by  that  alone.  The  action  of  these  sec- 
ondary causes,  however,  is  obviously  irregular,  pro- 
ducing retrogression  quite  as  frequently  as  progres- 
sion, and  causing  those  fluctuations  which  are  so 
characteristic  of  the  growth  of  nature ;  but  who 
can  fail  to  see  that  during  the  geological  ages 
there  has  been  a  great  advance,  and  the  present 
•  complex  result,  which  we  call  nature,  with  all  its 
intricate  adjustments  and  relations,  can  be  no 'more 
rationally  ascribed  to  the  causes  which  have  pro- 
duced variations  of  details,  however  great,  than  can 
the  mechanism  of  a  clock  be  referred  to  the  cir- 
cumstances which  in  different  localities  have  often 
determined  large  and  important  changes  in  the  ma- 
terials or  plan  of  its  construction. 

I  repeat,  therefore,  no  development  theory  can 
impair  the  evidence  of  design,  for  that  evidence  is 
based  on  facts  wholly  independent  of  any  theory  of 
cosmogony,  and  to  which  all  theories  must  conform. 
If  they  do  not,  they  will  inevitably  fall.  The  diffi- 
culty, to  my  mind,  in  Mr.  Darwin's  particular  theory, 
is  not  in  its  development  feature,  nor  in  its  princi- 
ple of  "  natural  selection  "  as  a  proximate  cause  of 
variation  in  species,  but  in  the  at  least  tacit  assump- 
tion made  by  so  many  of  its  advocates  that  this 
principle  is  the  one  and  only  efficient  cause  of  the 


254  THE  FINAL  CRITERION. 

resulting  adaptations  In  nature.  As  a  temporary- 
mode  of  correlating  facts,  and  as  a  working  hy- 
pothesis which  has  pointed  out  fruitful  lines  of  in- 
vestigation, the  theory  of  Mr.  Darwin  must  be  re- 
garded as  one  of  the  most  important  contributions 
to  modern  science;  but  a  naturalist  must  ignore  the 
whole  history  of  physical  science  who  would  claim 
that  this  theory  was  more  than  a  very  partial  truth, 
and  unless  it  can  be  shown  that  it  is  consistent 
with  the  action  of  an  intelligent  first  cause,  it  will 
soon  be  forgotten  like  those  that  have  gone  before  it. 
This  is  the  criterion  by  which  all  such  theories  are 
finally  judged  after  the  excitement  of  the  controversy 
by  which  they  were  heralded  has  passed,  and  after 
the  common  sense  of  mankind  has  settled  down  upon 
its  sober  second  thought.  Let  us  insist  that  all 
theories  of  cosmogony  shall  be  judged  on  their  own 
merits  as  scientific  theories,  but  let  us  also  insist 
that  they  shall  be  kept  within  their  own  sphere,  and 
not  allowed  to  have  a  voice  in  questions  of  religious 
faith,  on  which  they  have  absolutely  no  bearing. 
That  they  have  an  injurious  influence  while  they 
last,  is  frequently  more  the  fault  of  the  secondary- 
advocates  than  of  the  principals  in  the  dispute,  and 
we  must  not  expect  to  cure  the  evil  by  indiscrimi- 
nate censure  or  by  social  excommunication.  So  long 
as  man  thinks,  he  will  speculate ;  and  I  rejoice  that 
neither  political  nor  ecclesiastical  tyranny  can  touch 
this  prerogative  of  free  thought.  The  true  remedy 
consists  in  exposing  the  fallacy  of  the  shallow  phi- 
losophy which  is  so  ready  to  bring  forward  these 
crude  speculations  as  proofs  of  materialism,  and  also 


FIRM   BASIS   OF  THE   ARGUMENT.  255 

in  diffusing  among  educated  people  more  spiritual 
views  of  nature  and  its  laws. 

To  this  subject  I  shall  return  in  the  next  chap- 
ter. But  so  far  as  the  argument  for  design  is  con- 
cerned, all  these  considerations  are  unnecessary. 
The  evidence  is  so  ample,  that  we  can  afford  to 
waive  all  that  part  of  it  which  has  been  called  in 
question  by  the  progressionists,  without  weakening 
in  the  slightest  degree  the  force  of  the  argument. 
Before  the  first  organic  cell  could  exist,  and  before 
Mr.  Darwin's  principle  of  natural  selection  could 
begin  that  work  of  unnumbered  ages  which  was  to 
end  in  developing  a  perfect  man,  nay,  even  before 
the  solid  globe  itself  could  be  condensed  from  La- 
place's nebula,  the  chemical  elements  must  have 
been  created,  and  endowed  with  those  properties 
by  which  alone  the  existence  of  that  cell  is  rendered 
possible. 

But  although,  for  the  sake  of  argument,  we  might 
yield  to  the  progressionists  all  those  examples  of 
adaptation  which  they  claim  to  explain  by  their  the- 
ories, such  a  concession  is  really  of  no  value.  The 
parts  of  nature,  as  we  have  seen,  are  so  intimately 
linked  together  that,  if  there  be  design  anywhere, 
there  is  design  everywhere ;  and  as  the  structure  of 
the  human  body  was  prefigured  by  the  earliest  verte- 
brate forms  buried  in  the  geological  strata,  so,  and  as 
unquestionably,  the  whole  scheme  of  organic  life  was 
prefigured  in  the  gases  composing  the  atmosphere. 
If,  therefore,  I  have  proved  that  there  is  evidence 
of  design  in  the  constitution  of  the  atmosphere,  I 
have  also  proved  that  the  whole  scheme  of  nature  is 


2S6  HONEST  DOUBTS. 

the  result  of  Divine  Intelligence,  and  that  the  great 
argument  of  natural  theology  rests  on  a  basis  which 
no  present  theories'^  of  development  can  touch.  To 
show  that  there  is  evidence  of  design  in  these  stones 
of  nature's  edifice  has  been  my  chief  object  in 
this  book.  It  has  been  my  constant  aim  to  set 
forth  in  a  clear  light  the  startling  fact  that  the 
footprints  of  the  Creator  are  nowhere  more  plainly 
visible  than  on  that  very  matter  which  the  materi- 
alists so  vainly  worship,  and  if  I  have  thus  been  able 
to  remove  doubts  from  the  mind  of  any  honest 
seeker  after  God,  I  shall  feel  that  my  labor  has  not 
been  lost. 

But  however  earnest  the  purpose  or  sincere  the 
convictions,  the  spectres  of  our  doubts  will  some- 
times return,  and  hover  around  these  evidences  of 
our  faith.  Treat  them  not  lightly  either  in  yourself 
or  in  those  you  love.  Respect  all  honest  doubts ; 
for  it  is  the  noblest  natures  which  feel  them  and 
suffer  most.  His  must  be  a  dull  heart  which  is  not 
sometimes  appalled  by  the  mystery  of  our  being. 
Remember,  however,  that  these  doubts  are  from 
within,  not  from  without.  They  are  the  offspring  of 
your  fears,  and  not  of  your  science.  The  evidence 
is  ample.  It  is  more  faith  that  you  need.  Fight, 
then,  these  spectres  of  your  mind  as  the  enemies  of 
your    peace,   not    with    doubtful    disputations,   but 

*  We  of  course  refer  only  to  such  theories  and  speculations  as  are 
based  on  observed  facts  ;  for  no  others  are  worthy  of  serious  consid- 
eration. Science  has  not  as  yet  gone  one  step  behind  the  chemical  ele- 
ments, and  until  it  has,  no  speculations  in  regard  to  a  primordial  con- 
dition of  matter  can  have  any  bearing  on  our  subject. 


HONEST  DOUBTS.  2$/ 


with  earnest  thought  and  prayer,  and  Power  shall 
be  with  you 

"  in  the  night, 
Which  makes  the  darkness  and  the  light, 
And  dwells  not  in  the  night  alone."* 

*  Read  in  this  connection  Canto  cxxii.  of  the  **  In  Memoriam." 


CHAPTER  IX. 

ARGUMENT  FROM  GENERAL  PLAN. 

It  has  been  my  object  in  the  previous  chapters 
of  this  work  to  develop  before  you  the  great  argu- 
ment of  Natural  Theology  as  it  is  presented  by  the 
atmosphere.  I  have  endeavored  to  show  that  there 
is  abundant  evidence  of  design,  even  in  the  proper- 
ties of  the  chemical  elements,  and  hence  that  the 
argument  rests  upon  a  basis  which  no  present  theo- 
ries of  development  can  shake.  Having  dwelt  upon 
the  argument  from  special  adaptations  at  as  great 
length  as  my  plan  will  permit,  I  wish  in  this  chapter 
to  present  another  class  of  evidences  of  the  Divine 
attributes,  which,  although  less  conspicuous,  may  be 
even  more  impressive  to  some  minds  than  those  we 
have  studied.  The  indications  of  an  Infinite  Intelli- 
gence are  not  only  to  be  found  in  the  adaptations 
of  nature,  but  they  also  appear  in  the  grand  laws  by 
which  the  whole  material  universe  is  directed. 

I  am  well  aware  that  the  laws  of  nature,  so  far 
from  being  regarded  as  evidences  of  the  existence 
of  a  beneficent  God,  are  felt  by  many  minds  to  be 
actual  hinderances  to  their  faith.  They  are  thought 
to  give  to  the  whole  scheme  of  nature  a  mechanical 

258 


DEFINITION   OF  PHYSICAL  LAWS.  259 

aspect,  and  to  be  inconsistent  with  belief  in  a  super- 
intending Providence.  I  also  know  that  there  are 
many  scientific  men  who  regard  the  laws  of  nature 
as  the  manifestation  of  blind  physical  forces,  and 
who  recognize  a  Providence,  if  at  all,  only  in  the 
very  few  recorded  instances  where  the  normal  action 
of  these  forces  has  been  averted  by  a  special  mi- 
raculous interposition.  But  even  admitting  this  phi- 
losophy, still  I  think  it  will  appear  that  these  laws 
bear  so  conspicuously  the  marks  of  Intelligence,  and 
are  so  analogous  to  the  results  of  human  thought, 
that  we  cannot  resist  the  conclusion  that  they  were 
originally,  at  least,  ordained  by  an  intelligent  Crea- 
tor, or,  in  other  words,  that  the  laws  of  nature  are 
the  thoughts  of  God.  For  myself,  I  regard  the 
laws  of  nature  as  the  most  direct  evidence  possi- 
ble of  Infinite  wisdom,  and  it  will  be  my  object  to 
show  that  this  opinion  is  sustained  by  the  strongest 
analogies. 

Regarded  from  a  scientific  point  of  view,  physical 
laws  are  merely  our  human  expressions  of  that  order 
which  we  discover  in  the  material  universe.  In  its 
highest  form,  the  law  is  capable  of  a  precise  quanti- 
tative statement,  and  gives  the  basis  for  mathe- 
matical calculation  and  prediction.  Thus  the  law 
of  gravitation  enables  the  astronomer  to  calculate 
what  will  be  the  position  of  the  bodies  of  the  solar 
system  at  any  future  epoch,  and  to  predict,  almost 
to  the  very  second,  the  exact  time  when  an  eclipse 
will  begin,  and  what  will  be  the  precise  path  of  its 
shadow  over  the  earth.  The  greater  part  of  the 
laws  of  nature  do  not,  however,   admit  of  precise 


26o  DEFINITION  OF  PHYSICAL  LAWS.     • 

mathematical  statement,  and  are  merely  the  expres- 
sions of  the  order  which  has  been  observed  in  the 
phenomena  of  nature,  whether  in  respect  to  form, 
in  respect  to  number,  or  in  any  other  particular.  It 
is  convenient  to  distinguish  these  merely  phenomenal 
laws  from  the  higher  class,  which  are  usually  called 
dynamical ;  but  the  distinction  is  an  artificial  one, 
for  it  is  probable,  at  least,  that  in  all  cases  the 
phenomenal  laws  are  merely  the  phases  of  some 
higher  dynamical  law  not  yet  discovered.  More- 
over, if  we  believe  that  all  phenomena  are  direct 
manifestations  of  the  Divine  Will,  then  there  is  no 
law  apart  from  God.  His  action  is  not  necessitated 
or  prescribed  by  any  conditions,  even  although  im- 
posed by  Himself.  He  is  constantly  acting  in  nature, 
consciously  and  freely ;  but  He  acts  uniformly,  con- 
sistently, and  with  a  plan,  because  He  is  omniscient 
and  omnipotent.  Man  acts  with  inconstancy,  be- 
cause he  is  a  finite  being,  and  must^  be  guided  by 
probabilities  ;  but  with  God,  w^ho  seeth  the  end  from 
tiTe  beginning,  there  is  no  "variableness,  neither 
shadow  of  turning.'* 

The  whole  material  universe  may  then  be  re- 
garded as  the  manifestation  of  one  grand  compre- 
hensive creative  thought,  which  God  is  slowly  work- 
ing out  in  nature.  To  study  this  thought  in  all  its 
details  is  the  prerogative  of  man,  and  this  study  has 
been  the  appointed  means  of  cultivating  his  intellect 
and  elevating  his  condition.  From  time  to  time  the 
more  gifted  students  have  caught  glimpses  of  parts 
of  the  grand  thought,  and  these  glimpses  we  call 
laws ;  but  even  the  law  of  gravitation,  the  most  per- 


IDEA  OF   SYMMETJ...  ,   ,        -  . 


f 


feet  of  all,  is  felt  to  be  but  a  partial  f a^^  ana'  we         ^/ 
look    confidently  for  the  discovery  of  a  Widfep .  law /' , 
which  will  comprehend  Newton's  great  discover)^ as         ^ 
one  only  of  its  manifestations.     Let  us  now,  in  ordfery 
to  elucidate  and  confirm  this  simple  doctrine,  com-  ^ 
pare  some  of  the  laws  of  nature  with  the  results  of 
human  thought,  and,  whatever  may  be  our  theory  of 
causation,  we   cannot   but   be    impressed   with  the 
striking  analogy  between  the  two. 

The  idea  of  symmetry  is  inherent  in  every  human 
mind.  It  may  be  more  or  less  cultivated  by  experi- 
ence, but  the  germs  of  the  idea  are  found  even  in 
the  savage.  However  rude  his  condition,  man  is 
pleased  with  a  symmetrical  disposition  of  objects, 
and  his  taste  is  offended  when  the  laws  of  sym- 
metry are  grossly  violated,  although  he  may  have 
no  name  for  the  idea.  Corresponding  with  this 
idea  in  our  minds,  we  find  symmetry  everywhere  m 
nature.  The  parts  of  an  animal  are  symmetrically 
arranged  around  the  body,  and  the  leaves  of  a  plant 
are  symmetrically  disposed  around  the  stem,  but 
nowhere  in  nature  is  the  idea  of  symmetry  so  fully 
developed  as  in  the  mineral  kingdom. 

Almost  every  solid  substance,  when  slowly  depos- 
ited from  a  liquid  or  aeriform  condition,  assumes 
a  definite  symmetrical  shape  which  is  peculiar  to 
the  substance.  These  symmetrical  forms  are  called 
crystals,  and  the  process  by  which  they  are  ob- 
tained is  called  crystallization.  Freedom  of  motion 
— such  as  the  particles  of  matter  have  in  the  fluid 
state  —  is  an  essential  condition  of  crystallization. 
Moreover,  as  the  substance  becomes  solid,  the  par- 


262  IDEA   OF   SYMMETRY. 

tides  must  have  sufficient  time  to  arrange  themselves 
in  accordance  with  the  tendency  of  the  molecular 
forces,  and  the  longer  the  time  occupied  in  the 
process  of  crystallization,  the  more  perfect  we  find 
the  crystals.  The  crystal  represents  the  natural 
condition  of  a  substance,  and  the  peculiar  form  is 
the  most  essential  and  characteristic  of  all  its  prop- 
erties. 

Crystals  are  always  polyhedrons,  that  is,  solids 
bounded  by  plane  faces.  Assuming  this  fact  of  ob- 
servation, geometry  teaches  that  the  relative  posi- 
tions of  the  faces  of  a  crystal  may  be  defined  by 
means  of  three  straight  lines  not  all  in  one  plane,  but 
crossing  each  other  at  a  single  point.  These  lines 
are  called  axes,  and  the  common  point  is  called  their 
origin.  Now,  we  can  easily  conceive  of  all  the  pos- 
sible ways  in  which  three  such  lines  can  be  arranged, 
and  although  the  number  of  possible  variations  is 
evidently  infinite,  yet  they  can  all  be  classified  under 
a  few  categories.  Again,  taking  in  turn  each  of  these 
systems  of  axes,  as  they  are  called,  we  can  read- 
ily arrange  planes  symmetrically  around  the  three 
lines  selected  for  reference,  and  thus  by  a  process  of 
pure  thought,  with  no  other  guide  than  the  idea  of 
symmetry  as  it  exists  in  our  minds,  we  can  develop 
the  corresponding  geometrical  forms,  and  it  is  these 
forms,  and  these  alone,  which  we  find  on  actual  crys- 
tals. Moreover,  the  systems  of  possible  axes  corre- 
spond to  the  families  under  which  these  crystals  are 
naturally  classified. 

In  the  first  edition  of  this  book,  I  attempted  to 
illustrate  the  truth  we  are  discussing  by  showing 


IDEA   OF   SYMMETRY.  263 

how  the  forms  of  what  in  crystallography  is  called 
the  regular  system,  may  be  developed  by  arranging 
planes  symmetrically  around  a  system  of  axes  con- 
sisting of  three  lines  of  equal  length  at  right  angles 
to  each  other  ;  but,  as  a  consequence  of  the  attempt 
to  popularize  the  subject,  the  illustration  was  neces- 
sarily imperfect,  and  it  became  evident  that  the 
conceptions  involved  could  only  be  made  intelligi- 
ble to  those  who  already  had  some  knowledge  of 
crystallography.  I  shall  therefore,  in  the  present 
volume,  leave  to  the  student  the  task  of  investigating 
the  details,  and  simply  make  the  following  general 
statements.  Crystals  may  be  studied  from  two 
points  of  view :  first,  as  products  of  pure  thought, 
like  the  solids  of  geometry;  secondly,  as  objects  of 
natural  history;  and  the  specimens  found  in  nature 
correspond,  as  far  as  they  have  been  observed,  to 
the  deductions  of  geometry.  Furthermore,  the  lines 
which  we  use  in  constructing  mentally  the  theoretical 
forms  are  directions  which  in  the  actual  crystals  are 
distinguished  by  well  defined  physical  relations. 

The  products  of  Nature's  laboratory  correspond, 
then,  exactly  to  the  results  of  our  own  thoughts ; 
and  how  can  we  resist  the  conclusion  that  they  are 
the  manifestations  of  the  thoughts  of  an  intelligent 
Creator  ?  In  the  language  of  science,  the  crystal  is 
said  to  obey  the  law  of  symmetry  ;  but  obviously 
this  law  is  merely  the  reflection  of  the  same  simple 
idea  which  exists  in  our  own  minds,  and  which  must 
have  previously  existed  in  the  mind  of  God.  The 
whole  science  of  crystallography  is  a  development 
of  this  idea  of  symmetry.     Like  geometry,  it  is  a 


264  IDEA  OF  NUMBER. 


product  of  pure  thought,  and  its  truths  are  entirely 
independent  of  their  material  forms.  Indeed,  the 
mineral  kingdom,  so  far  as  it  is  known,  does  not  per- 
fectly represent  the  idea  of  symmetry,  even  as  it 
exists  in  the  human  mind.  There  are  possible  forms 
which  have  never  been  obtained  in  nature,  and  the 
science,  even  as  we  know  it,  could  never  have  been 
developed  by  observation  alone. 

By  following  out  the  simple  idea  of  symmetry, 
which  is  common  to  all  men,  we  have  found  that  the 
results  of  our  own  thought  perfectly  agree  with  the 
facts  of  nature.  Let  us  now  take  another  of  the 
primary  ideas  which  exist  in  the  human  mind,  and 
see  how  fully  that  is  realized  in  the  material  cre- 
ation. The  idea  of  number  is  as  inherent  in  the 
mind  as  that  oT  symmetry.  I  shall  not  attempt  to 
discuss  its~dngih "  or  trace  its  development ;  but  as- 
suming, as  all  will  admit,  that  the  results  of  human 
skill  constantly  exhibit  simple  numerical  relations, 
let  us  inquire  whether  the  same  characteristic  may 
not  be  discovered  in  nature. 

We  have  already  referred  to  the  well-known  prin- 
ciple that  the  position  of  a  plane  may  be  fixed  by 
means  of  three  straight  lines  or  axes  crossing  at  a 
common  point  called  the  origin.  If  the  plane  is  suf- 
ficiently extended  it  must,  of  course,  cross  each  of 
the  three  axes  either  at  a  finite  or  at  an  infinite  dis- 
tance from  the  origin,  and  if  these  distances,  which 
we  call  "  parameters,"  are  measured  or  calculated,  the 
position  of  the  plane  is  defined.  Again,  on  the  crystals 
of  many  substances — for  example  on  those  of  the  well- 
known  minerals  quartz,  calcite,  and  barite — we  find  a 


RATIO   OF  PARAMETERS.  265 

great  number  of  different  planes,  which,  if  not  on  any- 
single  crystal,  have  all  been  seen  on  the  different  crys- 
tals of  the  substance  that  have  been  examined.  If, 
now,  each  of  these  planes  is  defined  by  its  parameters, 
it  appears,  on  comparing  the  parameters  measured  on 
a  given  axis,  that,  for  crystals  of  the  same  substance, 
the  parameters  of  all  the  planes  are  simple  numerical 
multiples  of  each  other.  When  a  plane  is  parallel  to 
an  axis,  the  parameter  on  this  axis  is  of  course  infin- 
ity, and  this  is  the  most  commonly  occurring  case. 

As  an  illustration  of  the  law  we. are  considering, 
we  may  take  the  crystals  of  barite — the  mineralogi- 
cal  name  of  the  chemical  compound  called  baric  sul- 
phate. One  of  the  most  commonly  occurring  planes 
on  the  crystals  of  this  substance  has  parameters 
which,  when  measured  on  the  lines  usually  selected 
as  axes,  have  the  relative  values  a  :  b :  c  =  1.6107:  i : 
1.2276.  There  have  been  observed  on  crystals  of 
barite  no  less  than  thirty-four  different  planes,  and  in 
every  case  the  parameters  of  these  planes  conform  to 
the  expression  a^:  b':  c^  =  m  x  1.6107:  n  x  i :  px 
1.2276,  in  which  m,  n,  and  p  are  either  simple  whole 
numbers,  or  else  infinity.  Thus  we  have  for  m,  n, 
and  p  such  values  as  i22;  231 ;  112;  326;  142,  etc., 
and  similar  facts  are  true  of  the  crystals  of  any  other 
substance.  Indeed  this  law  of  simple  numerical 
ratios  is  the  fundamental  law  of  crystallography,  and 
gives  to  the  science  a  mathematical  basis. 

Similar  numerical  relations  appear  when  we  study 
the  formation  of  chemical  compounds.  I  have  al- 
ready defined  a  chemical  element  as  a  substance 
which  has  never  as  yet  been  decomposed,  and  all 


266  LAW   OF  DEFINITE   PROPORTIONS. 

the  matter  with  which  man  is  now  acquainted  is 
composed  of  one  or  more  of  at  most  seventy  ele- 
mentary substances.  When  two  of  these  elements 
unite  together  to  form  a  compound  body,  the  pro- 
portions in  which  they  combine  are  not  decided  by 
chance.  You  cannot  unite  these  elementary  sub- 
stances in  any  proportion  you  please.  The  propor- 
tion in  each  case  is  determined  by  an  unvarying  law, 
and  the  amounts  required  of  either  substance  are 
weighed  out  by  Nature  in  her  delicate  scales  with  a 
nicety  which  no  art  can  attain.  Thus,  for  example, 
23  ounces  of  sodium  will  unite  with  exactly  35.5 
ounces  of  chlorine ;  and  if  you  use  precisely  these 
proportions  of  the  two  elements,  the  whole  of  each 
will  disappear  and  become  merged  in  the  compound 
which  is  our  common  table  salt.  But  if,  in  attempt- 
ing to  make  salt,  we  bring  together  clumsily  23.5 
ounces  of  sodium  and  35.5  ounces  of  chlorine.  Na- 
ture will  simply  put  the  extra  half-ounce  of  sodium 
on  one  side,  and  the  rest  will  unite.  This  law,  which 
governs  all  chemical  combinations,  is  known  as  the 
"  law  of  definite  proportions." 

Tables  will  be  found  in  works  on  chemistry  which 
give,  opposite  to  the  name  of  each  elementary  sub- 
stance, a  numerical  value,  usually  called  its  atomic 
weight,  and  in  all  cases,  where  the  elements  are  capa- 
ble of  combining  with  each  other,  they  either  unite 
in  the  exact  proportions  indicated  by  these  numbers, 
or  else  in  some  simple  multiple  of  these  proportions. 

The  following  are  the  atomic  weights  which  are 
believed  by  the  author  to  have  been  determined 
with  the  greatest  accuracy : 


ATOMIC  WEIGHTS. 


267 


Aluminum 27.02 

Antimony 120.00 

Barium i37-i4 

Bromine 79-95 

Calcium 40.00 

Carbon 12.00 

Chlorine 35-46 

Hydrogen i.oo 

Iodine 126.85 

Lead 206.91 


Lithium   7.01 

Magnesium 24.00 

Nitrogen 14.04 

Oxygen 16.00 

Potassium 39- 14 

Phosphorus 31 -05 

Silver io7-93 

Sodium 23.05 

Sulphur ,  32.07 

Thallium 204.11 


These  values  are  called  atomic  weights  because, 
according  to  our  modern  chemical  theory,  they  rep- 
resent the  relative  weights  of  the  ultimate  atoms  of 
the  elements.  If  this  be  the  case,  it  is  evident  that 
when  the  atoms  group  themselves  together  to  form 
the  molecules"^  of  various  substances,  the  elements 
must  combine  by  whole  atoms,  that  is,  in  the  propor- 
tion of  the  atomic  weights,  or  of  a  simple  multiple 
of  these  proportions  ;  and  thus  this  atomic  theory 
explains  the  law  of  definite  proportions. 

In  connection  with  this  table  a  most  remarkable 
fact  should  be  noticed,  which  indicates  the  deep 
significance  of  this  series  of  values.  They  are  all 
mutually  dependent,  so  that  the  same  numbers 
which  represent  the  proportions  in  which  two  ele- 
mentary substances  combine  with  the  same  quantity 
of  a  third  substance,  represent  also  the  proportion, 
or  a  multiple  of  the  proportion,  in  which  they  com- 

*  The  molecule  of  a  substance  is  the  smallest  mass  of  the  substance 
that  can  exist  by  itself,  and,  when  subdivided,  it  breaks  up  into  ele- 
mentary atoms,  which,  however,  at  once  group  themselves  to  form 
new  molecules. 


268  PROUT*S   HYPOTHESIS. 

bine  with  each  other.  Thus  not  only  do  i6  parts  of 
oxygen  combine  either  with  1 2  parts  of  carbon  or  with 
14  parts  of  nitrogen  to  form  in  the  first  case  carbonic 
oxide,  and  in  the  second  case  nitric  oxide,  but  also 
12  parts  of  carbon  combine  with  14  parts  of  nitro- 
gen to  form  cyanogen  ;  and  the  same  principle  holds 
for  the  other  weights  given  in  the  table,  when- 
ever the  elements  are  capable  of  combining,  al- 
though, in  most  cases,  only  the  multiple  values 
appear  in  the  formation  of  known  compounds. 

The  standard  of  these  weights  is  of  course  arbi- 
trary ;  but  if  one  number  stands  for  pounds,  all  the 
rest  stand  for  pounds,  or  if  one  stands  for  ounces,  all 
the  rest  stand  for  ounces.  It  is  usual,  however,  to 
leave  the  standard  indefinite,  and  speak  of  so  many 
parts.  Again,  the  weights  have  only  relative  values ; 
but  if  we  give  to  any  one  a  definite  value,  all  the 
rest  assume  definite  values.  Our  units  must  neces- 
sarily be  more  or  less  arbitrary.  Most  chemists  take 
hydrogen  for  the  unit  of  weight,  and  the  numbers 
given  in  the  table  express  the  atomic  weights  of 
the  other  elements  calculated  on  this  assumption. 
But  we  might  take  any  one  of  the  elem.ents  as  our 
starting-point,  and  formerly  the  European  chemists 
used  a  system  of  weights  calculated  on  the  as- 
sumption that  the  equivalent  of  oxygen  was  100. 
This  assumption  gives  an  entirely  different  system 
of  numbers ;  but  the  difference  is  of  no  practical  im- 
portance so  long  as  the  relative  values  remain  un- 
changed. 

Dr.  Prout  was  the  first  to  notice  that  many  of  the 
atomic  weights  were   simple  multiples   of  that   of 


PROUT^S  HYPOTHESIS.  269 

hydrogen,  and  he  thought  that,  if  the  weight  of 
hydrogen  was  taken  as  unity,  the  other  atomic 
weights  could  all  be  expressed  by  whole  numbers. 
The  progress  of  chemistry  for  a  long  time,  however, 
did  not  seem  to  confirm  this  view — since  most  of  the 
accurate  experiments  made  for  the  purpose  of  fixing 
these  constants  gave  incommensurable  values,  and 
this  was  especially  true  of  a  most  noteworthy  inves- 
tigation, undertaken  by  Professor  Stas,  of  Brussels, 
with  the  view  of  testing  Prout's  hypothesis.  His 
experiments,  which  were  conducted  with  extreme 
care,  and  with  very  large  amounts  of  material, 
gave  incommensurable  values,  and  the  results  were 
thought  at  the  time  to  show  that  the  hypothesis  in 
question  was  wholly  illusory.  Still  it  was  remark- 
able that  the  values  obtained  by  Stas  differed  from 
whole  numbers  only  by  a  small  fraction  of  a  unit, 
and  in  the  accurate  determinations  which  have  since 
been  made  by  other  chemists,  the  same  striking  feat- 
ure appears.  The  nineteen  atomic  weights,  whose 
values  are  given  in  the  above  table,  may  be  fairly 
considered  as  the  only  ones  which  have  been  deter- 
mined, with  reference  to  hydrogen,  with  the  greatest 
attainable  precision,  or  a  near  approach  thereto,  and 
it  will  be  noticed  that,  with  the  exception  of  the 
atomic  weight  of  chlorine,  the  values  differ  in  no  case 
from  a  whole  number  by  more  than  fifteen-hun- 
dredths  of  an  integer,  and  generally  by  much  less.  If 
the  atomic  weights  are  in  fact  whole  numbers,  such 
slight  differences  from  the  true  values  as  these  in 
the  observed  results  are  exactly  what  we  should 
expect,  seeing  that  no  determinations  of  this  kind 


270  LAW   OF   MULTIPLE   PROPORTIONS. 

can  with  certainty  be  freed  from  the  influence  of 
constant  experimental  errors.  On  the  other  hand, 
if  the  true  weights  are  incommensurable  and  distrib- 
uted by  chance,  the  probability  that  the  observed 
values  would  all  lie  so  near  to  whole  numbers  as 
they  do  would  be  exceedingly  small,  and  hence  the 
total  result,  as  far  as  it  goes,  may  be  said  to  confirm 
rather  than  invalidate  Prout's  hypothesis.  But  leav- 
ing this  question  to  be  decided  by  further  investiga- 
tion, let  us  turn  to  an  allied  class  of  facts,  which 
exhibit  a  very  simple  numerical  relation,  that  can- 
not be  questioned,  and  which,  indeed,  by  analogy 
furnish  a  certain  presumption  in  favor  of  the  hypo- 
thesis of  Prout. 

In  very  many  cases  the  same  elements,  by  uniting 
in  different  proportions,  form  several  distinct  com- 
pounds, and  we  invariably  find  that  the  proportions 
of  the  elements  in  the  different  compounds  bear  a 
very  simple  numerical  relation  to  each  other.  Thus 
there  are  five  compounds  of  oxygen  and  nitrogen, 
which  contain  these  elements  in  the  proportions 
indicated  in  the  following  table. 

Compounds  of  Oxygen  and  Nitrogen, 

Nitrogen.  Oxygen. 

Nitrogen  Monoxide 14  parts.  8  parts. 

Nitrogen  Dioxide 14     "     8x2  =  16      " 

Nitrogen  Trioxide 14     "     8  x  3  =  24      " 

Nitrogen  Tetroxide 14     "     8  x  4=32      " 

Nitrogen  Pentoxide 14     "     8x5  =40      " 

It  will  be  noticed  that  the  proportions  of  oxygen  in 


LAW   OF   MULTIPLE   PROPORTIONS.  2/1 

these  compounds  are  in  all  cases  simple  multiples  of 
eight,  the  proportion  in  the  first.  In  like  manner, 
the  compounds  of  manganese  with  oxygen  show 
similar  relations. 

Compounds  of  Oxygen  and  Manganese. 

Manganese.        Oxygen. 

Manganese  Monoxide 27.5  parts.  8  parts. 

Red  Manganese  Oxide 27.5     "     io|==8  x  \\     " 

Manganese  Sesquioxide 27.5     "     12   =8xi|-     " 

Manganese  Dioxide 27.5     "     16  =8x2       " 

Manganese  Heptoxide 27.5     "     28  =8  x  3J     " 

The  relation  is  not  quite  so  simple  as  in  the  other 
case,  but  still  the  same  general  truth  is  evident,  and 
these  two  examples  are  fair  illustrations  of  what  has 
been  observed  throughout  the  whole  range  of  chem- 
ical compounds.  Thus  we  find  in  these  elementary- 
forms  of  matter — the  blocks  with  which  the  universe 
has  been  built — the  same  simple  numerical  relations 
which  everywhere  appear  in  the  constructions  of  man. 
Similar  numerical  relations  are  found  throughout 
the  whole  universe  of  matter.  In  the  solar  system, 
for  example,  with  the  exception  of  Neptune,  the 
intervals  between  the  orbit  of  Mercury  and  the 
orbits  of  the  other  planets  go  on  doubling,  or  nearly 
so,  as  we  recede  from  the  Sun.  Thus  the  interval 
between  the  Earth  and  Mercury  is  nearly  twice  as 
great  as  that  between  Venus  and  Mercury,  the 
interval  between  Mars  and  Mercury  nearly  twice 
as  great  as  that  between  the  Earth  and  Mercury, 
and  so  on.  Again,  if  we  compare  the  periods  of 
revolution  around  the  Sun,  expressed  in  days,  we 


2/2  LAW   OF  PERIODIC  TIMES. 

shall    find    another   simple    numerical    relation,    as 
shown  by  the  following  table. 

Law  of  Periodic  Times. 

Observed.  Theoretical.  Fractions. 

Neptune 60,129  62,000 

Uranus 3o>687  31,000  \ 

Saturn io,759  ^^^ZZZ  \ 

Jupiter 4,333  4,133  I 

Asteroids 1,200  to  2,000       1,550  f 

Mars 687  596  -f^ 

Earth 365  Z^^^^X  _s 

Venus 225  227  l^f  )  ^^ 

Mercury 88  87  \l 

It  will  be  noticed  that  the  period  of  Uranus  is  \ 
that  of  Neptune,  the  period  of  Saturn  \  that  of 
Uranus,  the  period  of  Jupiter  about  f  that  of  Saturn, 
the  period  of  the  Asteroids  about  f  that  of  Jupiter, 
the  period  of  Mars  about  -^  that  of  the  Asteroids, 
the  period  of  Venus  about  /y  that  of  Mars,  and  the 
period  of  Mercury  about  if  that  of  Venus.  The 
successive  fractions  are  very  simply  related  to  each 
other,  as  will  at  once  appear  on  writing  them  in  a 
series, 

112      3        5  8        1J?      /?rr 

Notice  that,  after  the  first  two,  each  succeeding 
fraction  is  obtained  by  adding  together  the  numera- 
tors of  the  two  preceding  fractions  for  a  new  numera- 
tor, and  the  denominators  for  a  new  denominator. 
From  this  series,  however,  the  Earth  is  excluded. 
Its  time  of  revolution  is  almost  exactly  -^^  of  that 


LAW   OF   PHYLLOTAXIS.  2/3 

of  Mars,  and  that  of  Venus  nearly  -|f  of  that  of  the 
Earth  ;  but  although  these  fractions  do  not  fall  into 
the  above  series,  they  are  members  of  a  comple- 
mentary series  beginning 

This  simple  relation  was  discovered  by  Professor 
Peirce,  and  he  has  proposed  an  explanation  for  the 
anomaly  presented  by  the  Earth.  But  it  is  not 
important  to  dwell  on  this  point.  My  only  object 
has  been  to  show  that  simple  numerical  relations  ap- 
pear in  the  planetary  system,  and  this,  as  I  trust, 
has  been  fully  illustrated. 

Passing  now  to  the  vegetable  kingdom,  we  fina 
again  the  same  numerical  laws.  The  leaves  of  a 
plant  are  always  arranged  in  spirals  around  the 
stem.  If  we  start  from  any  one  leaf,  and  count  the 
number  of  leaves  around  the  stalk  and  the  number 
of  turns  of  the  spiral  until  we  come  to  a  second  leaf 
immediately  over  the  first,  we  find  that  for  any  given 
plant,  as  an  apple-tree  fqr  example,  the  number  of 
leaves  and  the  number  of  turns  of  the  spiral  are  al- 
ways absolutely  the  same.  The  simplest  arrange- 
ment is  where  the  coincidence  occurs  at  the  second 
leaf,  after  a  single  turn  of  the  spiral ;  and  this  may 
be  expressed  by  the  fraction  ^,  whose  numerator  de- 
notes the  number  of  turns  of  the  spiral,  and  whose 
denominator  the  number  of  leaves.  The  next  sim^ 
plest  arrangement  is  when  the  coincidence  occurs  at 
the  third  leaf,  after  a  single  turn  of  the  spiral,  and 
may  be  expressed  by  the  fraction  i.  These  two 
fractions  express  respectively  the  greatest  and  the 


274 


LAW   OF  PHYLLOTAXIS. 


smallest  divergence  between  two  successive  leaves 
which  has  been  observed.  The  angle  between  two 
successive  leaves,  therefore,  is  never  greater  than 
1 80°,  or  half  the  circumference  of  the  stem,  and 
never  less  than  120^,  or  one-third  of  the  circumfer- 
ence. The  arrangement  next  in  simplicity  is  where 
the  coincidence  occurs  at  the  fifth  leaf,  after  two 
turns  of  the  spiral,  as  is  represented  in  the  preced- 
ing figures.     Other  examples  are  given  in  the  table 

Law  of  Phyllotaxis  (Leaf -Arrangement), 


Name  of  Plant. 

Number  of 

Turns 
of  Spiral.* 

Number  of 
Leaves.* 

Fraction, 

Angle  of  Divergence 

between  two 
successive  Leaves. 

Grasses      

I 
I 

2 
3 

5 

8 

13 
21 

2 
3 

5 

8 

13 

21 

34 

55 

1 
f 
-1% 

180" 
120° 

144° 

135° 
138°  28' 

137°  9' 

137°  39' 
137°  27' 

137°  30'  28" 

Sedges   

Apple,     ) 

Cherry,    \ 

Poplar,    ) 
Holly,            ) 

Callistemon,  >• 

Aconite,         ) 
Rosettes  of  the  1 

Houseleek,      1    , , 
Cones  of  the      | 
White  Pine,     J 
Cones  of  the  Euro- ) 
pean  Larch,       \ 
Certain  Pine  Cones, 
Certain  Pine  Cones, 

Typical  arrangement  which  would  expose  to  the   . 
Sun's  rays  the  greatest  leaf-surface, 

which  follows,  and  it  will  be  seen  that  we  have  pre- 
cisely the  same  series  of  fractions  in  the  arrange- 
ment of  leaves  around  the   stem  of  a  plant  which 

*  Before  a  leaf  occurs  vertically  over  the  first. 


ARGUMENT  FROM   GENERAL  PLAN.  2/5 

appears  in  the  periods  of  the  planets.  The  fractions 
of  this  series  are  all  gradual  approximations  to  a 
mean  fraction  between  ^  and  |,  which  would  give 
the  most  nearly  uniform  distribution  possible  to  the 
leaves,  and  expose  the  greatest  surface  to  the  sun. 

But  this  law  does  not  stop  with  the  plants.  The 
same  series  of  fractions  expresses  also  the  spiral 
arrangement  of  the  tentacles  of  the  Polyp  and  of  the 
spines  of  the  Echinus.  Thus  through  the  whole 
realm  of  nature,  from  the  structure  of  the  crystals  to 
the  dimensions  of  the  human  form,  a  similar  numeri- 
cal simplicity  is  preserved. 

Have  you  never  recognized  the  composition  of 
your  friend  in  some  anonymous  literary  article,  by  a 
peculiar  phraseology,  a  turn  of  style,  or  a  method  of 
thought  which  no  artifice  could  conceal  ?  Have  you 
never  felt  a  glow  of  pleasure  when  you  unexpectedly 
discovered  on  the  walls  of  a  picture-gallery  the  work 
of  a  well-known  artist,  marked  by  some  peculiarity 
of  grouping  or  coloring?  Has  your  attention  never 
been  quickened  when  an  orchestra  has  suddenly 
struck  into  a  new  theme  of  a  favorite  composer, 
never  heard  before,  but  unquestionably  his?  If  you 
have  experienced  these  or  similar  emotions,  you 
know  something  of  the  force  with  which  such  nu- 
merical laws  impress  the  mind  of  the  student  of 
nature,  and  you  also  know  how  difficult  it  is  to  make 
the  power  of  such  impressions  understood.  I  wish 
I  could  givQ  you  a  full  conception  of  this  power ; 
for  you  cannot  otherwise  feel  the  full  force  of  the 
evidence  which  these  facts  afford.  They  point  di- 
rectly to  an  intelligence  in  nature  like  our  own,  and 


276     ARGUMENT  FROM  GENERAL  PLAN. 

they  are  a  seal  to  the  declaration  of  the  Bible,  that 
man  was  created  in  the  image  of  his  God. 

The  broken  porticoes  of  the  Parthenon  still  stand 
on  the  Acropolis  at  Athens  to  incite  the  imitation 
and  win  the  admiration  of  the  architect.  That  beau- 
ty of  outline  and  those  faultless  proportions,  which 
modern  art  has  copied  but  never  excelled,  all  depend 
on  an  exact  conformity  of  all  the  parts  to  the  laws 
of  symmetry  and  to  simple  numerical  ratios.  We 
justly  regard  that  ruined  temple  as  the  evidence  of 
the  highest  intelligence  ;  and  when  we  find  the  same 
symmetry,  the  same  numerical  ratios,  appearing 
everywhere  in  nature,  how  can  we  refuse  to  admit 
that  they  also  are  the  evidence  of  intelligence  and 
thought  ?  Moreover,  since  the  laws  of  symmetry 
and  number  pervade  the  whole  universe,  from  the 
structure  of  the  solar  system  down  to  the  organiza- 
tion of  a  worm,  they  prove,  if  they  prove  anything, 
that  the  whole  is  the  manifestation  of  the  thoughts 
of  the  one  great  Jehovah,  who  "  in  the  beginning  " 
created  all  things  by  the  word  of  His  power. 

I  have  thus  endeavored  to  show  that  the  laws  of 
nature,  so  far  from  proving  that  the  world  is  governed 
by  an  inexorable  necessity,  furnish  the  strongest  evi- 
dence of  an  overruling  mind.  We  must  be  careful, 
however,  not  to  misinterpret  this  evidence ;  for  an- 
alogies like  those  we  have  studied  led  Schelling  and 
the  philosophers  of  his  school  to  regard  outward 
nature  not  merely  as  the  result  of  Divine  Thought, 
but  as  identical  with  that  thought,  and  inseparable 
from  it.     Indeed,  there  are  many  among  us  who  re- 


ERROR   OF  PANTHEISM.  2// 

gard  the  material  universe  as  the  manifestation  of 
God,  in  the  same  intimate  sense  in  which  our  bodies 
are  the  manifestation  of  our  own  personality;  who 
therefore  believe  that  the  world  is  and  always  has 
been  a  part  of  His  Eternal  Being,  and  who  look 
upon  the  laws  of  nature  not  merely  as  the  mani- 
festation of  an  Infinite  Intelligence,  but  as  a  part  of 
that  Intelligence  itself. 

This  philosophy  may  be  made  to  appear  very 
attractive,  and  even  very  reverential ;  but  when  fol- 
lowed out  to  its  logical  consequences,  it  reduces  God 
to  the  level  of  nature,  and  merges  His  being  in  the 
matter  He  created..  We  must  be  as  careful  to  avoid 
the  snares  of  pantheism,  as  the  slough  of  material- 
ism. Both  are  equally  destructive  of  true  religion, 
and,  although  they  lie  on  opposite  sides  of  the  Chris- 
tian's path,  they  lead  to  the  same  result ;  and  if  once 
enticed  from  the  narrow  way,  the  Christian  will  be 
fortunate  if  Faith  rescues  him  from  the  peril  before 
he  falls  into  the  gulf  of  atheism.  We  must  not  con- 
found the  Creator  with  the  creature.  There  is  a  per- 
sonal God  above  all  and  over  all,  and  although  na- 
ture manifests  His  intelligence,  its  material  forms  are 
only  the  reflection,  not  the  substance,  of  His  Being. 
The  error  of  the  pantheist  arises  from  a  too  superficial 
study  of  nature,  and  if  we  examine  more  closely  the 
analogies  between  the  laws  of  nature  and  the  results 
of  human  thought,  I  am  confident  we  shall  find  that 
the  created  forms  may  be  readily  distinguished  from 
the  Intelligence  which  gave  them  being. 

In  every  human  work  we  may  always  distinguish 
two  things,  the  conception  and  the  execution,  and  the 


278  CONCEPTION  AND   EXECUTION. 

last  never  exactly  conforms  to  the  first.  For  ex- 
ample, in  one  of  the  grand  Gothic  cathedrals  of  our 
mother  country  we  see  united  in  the  plan,  first,  the 
idea  of  the  cross,  the  emblem  of  our  Christian  faith  ; 
then  the  spire,  typifying  the  aspiration  of  the  soul ; 
and  lastly,  the  long  aisles,  whose  pointed  arches  and 
delicate  tracery  have  been  copied  from  the  interlac- 
ing branches  of  God's  first  temple.  The  combina- 
tion of  these  ideas  may  be  said  to  be  the  conception 
of  the  cathedral ;  but  how  differently  has  this  con- 
ception been  embodied  in  the  numerous  cathedral 
churches  of  England  !  Besides  the  peculiar  caprices 
of  the  architect  or  builder,  we  can  trace  in  each 
church  an  evident  adaptation  of  the  parts  to  special 
purposes.  Here  a  "  lady  chapel  **  has  been  included 
in  the  design,  and  here  the  mausoleum  of  a  king  or 
a  prelate ;  here  a  portion  has  been  adapted  to  the 
reading  of  the  service,  and  here  to  the  session  of  the 
ecclesiastical  court ;  but  however  varied  the  execu- 
tion, the  same  conception  is  evident  in  all.  So  it  is 
in  all  architecture.  Our  modern  dwellings  are  built 
after  a  few  general  types,  and  the  conception  is  very 
nearly  the  same  in  all  houses  of  any  one  class.  But 
how  differently  a  skilful  architect  will  arrange  the 
details,  and  adjust  them  to  the  circumstances  of  the 
location,  to  the  wants  of  the  family,  or  the  taste  of 
the  owner!  and  no  one  knows  better  than  he  that 
the  conception  of  the  building  is  one  thing,  and  the 
execution  of  that  conception  a  very  different  thing. 

In  the  higher  forms  of  art,  the  same  truth  appears 
even  more  strikingly.  The  Transfiguration  of  Ra- 
phael, that  masterpiece  of  painting,  does  not  hold 


DISTINCTION   ILLUSTRATED.  279 

you  breathless  before  it  so  much  by  what  it  actually 
represents,  as  by  what  it  embodies  and  helps  you  to 
realize.  He  who  sees  merely  what  is  painted  on  the 
canvas  will  turn  away  disappointed,  but  in  the  soul 
of  the  true  student  of  art,  who  enters  into  the  spirit 
of  the  great  painter,  the  conception  grows  as  he 
gazes,  until  he  becomes  transported  and  gains  a 
vision  of  the  splendors  of  the  Mount.  In  like  man- 
ner, it  is  not  that  lovely  female  face  which  has  en- 
deared the  Sistine  Madonna  to  so  many  hearts,  and 
made  Dresden  one  of  the  shrines  of  the  world.  In 
mere  point  of  execution,  this  picture  may  be  sur- 
passed by  many  works  of  living  artists  ;  but  the  con- 
ception of  a  pure  mother's  love  has  been  nowhere 
embodied  as  there,  and  that  is  the  charm.  You 
stand  before  the  Laocoon  until  the  blood  runs  cold 
and  the  muscles  writhe  in  sympathy,  and  then  you 
look  at  the  motionless  statue  and  wonder  whence 
comes  the  power.  It  is  not  in  the  skilfully  chiselled 
marble,  but  it  is  in  the  conception  of  the  unknown 
artist,  which  the  petrified  forms  suggest.  So  it  is 
everywhere  with  the  works  of  man  ;  the  conception 
can  always  be  distinguished  from  the  embodied  fact. 
But  what  need  of  illustration  ?  Who  does  not  know 
the  difference  between  the  two,  and  who  has  not 
sadly  experienced  how  far  his  best  efforts  fall  short 
of  his  ideal?  The  thought,  the  conception,  how 
noble  !  the  execution,  the  reality,  how  humble ! 

Turning  now  to  Nature,  we  find  the  same  distinc- 
tion there  between  the  conception  and  the  facts.  Na- 
ture does  not,  of  course,  like  man,  fall  below  her  ideal 
for  want  of  power,  but  she  departs  from  it  in  order  to 


28o  ILLUSTRATED   BY   CRYSTALS. 

adapt  her  work  to  specific  ends,  or  to  accommodate 
it  to  conditions  and  accidents  of  various  kinds  ;  and 
everywhere  the  conception,  or,  as  we  generally  call 
it,  the  law,  is  modified  in  the  execution,  so  that  the 
actual  can  be  plainly  distinguished  from  that  which 
our  minds  have  recognized  as  the  ideal.  Review  for 
a  moment,  with  this  idea,  a  few  examples  of  nat- 
ural laws,  beginning  with  the  law  of  symmetry. 

We  seldom,  if  ever,  find  in  nature  crystals  having 
that  regularity  of  form  or  that  perfection  of  outline 
represented  in  our  figures.  Natural  crystals  are 
almost  invariably  more  or  less  distorted  or  imperfect, 
and  a  perfect  crystal  is  at  best  a  very  rare  excep- 
tion. It  is  true  that  in  all  cases  of  distortion  the 
relative  inclination  of  the  planes  is  very  nearly  con- 
stant ;  but  even  this  is  liable  to  a  slight  variation. 
Moreover,  many  of  the  ideal  forms  of  crystals  are 
never  found  in  nature,  or  if  at  all,  not  in  their  per- 
fection. They  are  at  best  merely  shadowed  forth, 
as  it  were,  on  other  forms,  and  so  partially  that  the 
unpractised  eye  would  never  detect  them.  So  true 
is  this,  that,  as  I  have  before  stated,  the  present 
science  of  crystallography  could  never  have  been 
developed  by  observation  alone.  How  evident, 
then,  the  distinction  between  the  actual  crystals  and 
the  thought  which  they  embody ! 

Crystallography  is  worthy  of  special  study  from 
this  point  of  view.  Of  all  the  departments  of  natural 
history  it  most  nearly  approaches  a  perfect  science. 
The  conceptions  involved  are  so  simple  that  they 
have  been  grasped  by  the  human  understanding 
with  a  completeness  which  has  nowhere  else  been 


ILLUSTRATED   BY    CHEMISTRY.  28 1  ^  {^ 


reached,  and  we  feel  confidence  that,  to  a  great  ex- 
tent at  least,  we  comprehend  the  plan.  Hence  in 
this  science  the  distinction  on  which  we  are  here  in- 
sisting becomes  plainly  marked,  but  of  course  the 
truth  can  be  realized  in  its  fulness  only  by  the  stu- 
dents who  have  mastered  the  subject. 

In  striking  contrast  to  the  completeness  of  the 
science  of  crystallography,  is  the  present  obviously 
rudimentary  condition  of  the  theory  of  chemistry  ; 
but  even  in  this  subject,  although  the  thought  has 
been  so  imperfectly  comprehended,  the  distinction 
between  the  governing  plan  and  the  material  mani- 
festation is  perfectly  clear.  The  various  attempts 
to  classify  the  chemical  elements  according  to  their 
natural  affinities  have  never  been  more  than  very  par- 
tially successful.  This  arises  chiefly  from  the  com- 
plex relationship  which  many  of  the  elementary 
substances  manifest,  and  different  authors  may  rea- 
sonably assign  to  such  elements  different  places  in 
their  system  of  classification,  according  as  they  chiefly 
view  them  in  one  or  the  other  aspect.  Indeed,  no 
classification  in  independent  groups  can  satisfy  the 
complex  relations  of  the  elements.  These  relations 
cannot  be  exhibited  by  a  system  of  parallel  series, 
but  only  by  a  web  of  crossing  lines,  in  which  the  same 
element  may  be  represented  as  a  member  of  two  or 
more  series  at  once,  and  as  affiliating  in  different 
directions  with  very  different  classes  of  substances. 

These  attempts  at  classification  have,  however, 
made  conspicuous  one  feature  in  the  scheme  of  the 
chemical  elements,  which  seems  to  be  fundamental. 
It  appears  that  as  the  atomic  weight  increases,  ele- 


282         SCHEME   OF  THE   CHEMICAL  ELEMENT. 

merits  having  closely  allied  properties  occur  at  nearly- 
regular  intervals,  so  that  with  Mendelejeff  we  can 
arrange  the  elements  in  the  order  of  their  atomic 
weights  in  a  series  of  horizontal  lines  containing 
each  about  seven  members,  and  bring  into  the  same 
vertical  columns  only  elements  which  belong  to  the 
same  natural  family,  or  at  least  are  allied  in  some 
respect.  Tables  of  the  elements  so  arranged  will  be 
found  in  most  of  the  recent  works  on  chemistry,^  but 
necessarily  the  scheme  is  intelligible  only  to  those 
who  are  already  familiar  with  the  properties  of  the 
elementary  substances,  and  it  would  be  out  of  place 
to  enter  into  the  details  in  this  book.  As  in  almost 
all  classifications  of  natural  objects,  the  observed 
facts  require  considerable  humoring  in  order  to 
accommodate  them  to  the  scheme,  and,  moreover,  the 
elements  that  are  brought  together  in  the  vertical 
columns  are  frequently  allied  by  only  one  set  of 
their  properties,  while  in  other  respects  they  are 
equally  or  even  more  closely  related  to  elements 
from  which  they  are  widely  separated  by  the  system. 
Still  no  one  who  studies  the  subject  can  fail  to  be 
impressed  with  the  general  fact  that  there  is  an 
orderly  recurrence  of  similar  qualities  in  the  series 
of  the  elements.  Moreover,  the  discovery  of  the 
new  element  gallium  has  filled  one  of  the  obvious 
gaps  in  the  series,  as  originally  constructed  by  Men- 
delejeff, and  the  qualities  of  this  remarkable  metal 
closely  conform  to  those  which  he  had  predicted  for 
the  missing  member  of  the  series  ;  furthermore,  some 

*  See  Roscoe  and  Schorlemmer's  Treatise,  Vol.  II.,  page  507. 


THE   RARE   ELEMENTS.  283 

of  the  irregularities  in  the  original  classification  have 
been  harmonized  by  redeterminations  of  doubtful 
atomic  weights. 

The  glimpses  that  we  have  thus  been  able  to  gain 
of  the  order  in  the  constitution  of  matter,  give  us 
grounds  for  believing  that  there  is  a  unity  of  plan 
pervading  the  whole  scheme,  and  encourage  a  con- 
fident expectation,  that  hereafter,  when  our  knowl- 
edge becomes  more  complete,  chemists  may  attain  to 
at  least  such  a  partial  conception  of  this  plan  as  will 
enable  them  to  classify  both  elementary  and  com- 
pound substances  under  some  natural  system  ;  and 
in  imagination  we  may  even  look  forward  to  the 
time  when  science  shall  succeed  in  expressing  all 
the  possibilities  of  this  scheme  in  a  few  general  for- 
mulae, which  will  enable  the  chemist  to  predict  with 
absolute  certainty  the  qualities  and  relations  of 
any  given  combination  of  materials  and  conditions. 
But  although  to  a  very  slight  extent  the  idea  has 
been  realized  for  the  compounds  of  carbon,  yet, 
as  a  whole,  this  grand  conception  is  to-day  only  a 
dream. 

There  is  a  point  connected  with  the  classification 
of  the  chemical  elements  which  is  deserving  of  our 
notice  in  this  connection.  We  have  already  seen 
that,  although  some  seventy  elements  have  been 
discovered — several  of  which,  however,  are  as  yet  of 
doubtful  authenticity — -the  greater  portion  of  the 
earth/s  crust  consists  of  only  ten  or  twelve.  In- 
deed, if  the  remaining  fifty  elements  were  suddenly 
annihilated,  the  mass  of  the  globe,  so  far  as  we  know, 
would  not  be  sensibly  diminished.     Indeed,  a  large 


284  THE   RARE   ELEMENTS. 

number  of  the  elements  occur  in  such  minute  quanti- 
ties that  they  can  be  detected  only  by  the  most  skil- 
ful chemical  analysis.  That  these  very  rare  elements 
were  designed  by  the  Creator  to  subserve  important 
ends,  we  need  not  doubt ;  but  it  is  certain  that  they 
play  a  very  subordinate  part  on  the  surface  of  the 
globe.  For  bromine  and  iodine,  and  a  few  others, 
important  applications  have  been  discovered  in  the 
arts  or  in  medicine ;  but  the  rest,  comprising  at 
least  one-third  of  all  the  known  elements,  have  no 
apparent  value  except  as  parts  of  a  general  plan. 
In  the  light  of  a  utilitarian  philosophy  they  must 
appear  useless  ;  but  to  the  true  student  of  nature 
they  have  a  significance  which  transcends  everything 
else.  They  are  parts  of  a  universal  order,  of  a  Di- 
vine cosmos,  which  would  be  incomplete  without 
them.  They  are  the  manifestation  of  Infinite  In- 
telligence. They  embody  the  thoughts  of  God.  In 
the  words  of  Chevalier  Bunsen,  "  Law  is  the  su- 
preme rule  of  the  universe,  and  this  law  is  intel- 
lect, is  reason,  whether  viewed  in  the  formation 
of  a  planetary  system  or  in  the  organization  of  a 
worm.'* 

But  we  must  remember,  in  discussing  this  ques- 
tion, that  it  does  not  follow,  because  we  cannot  dis- 
cover any  important  end  which  these  elements 
subserve  on  our  earth,  that  they  have  no  practical 
utility.  For  after  acknowledging  the  dignity  which 
they  acquire  when  regarded  as  the  characters  of  that 
language  in  which  the  creative  thoughts  have  been 
written,  and  as  the  appointed  means  of  educating 
the  human  race,  still   it  does  not   seem    consistent 


POSSIBLE   USES.  285 


with  that  economy  of  resources  which  appears  in  all 
parts  of  the  Divine  plan,  that  they  should  have  no 
special  functions  to  discharge  in  the  cosmos.  Now 
I  would  suggest,  but  I  offer  the  suggestion  in  all 
humility,  that  these  very  rare  elements  may  be 
adapted  by  their  peculiar  properties  to  the  thermal 
conditions  of  some  other  planet  or  some  other  stel- 
lar system.  We  have  seen  that  those  elements 
which  are  the  most  widely  distributed  over  the 
earth  are  such  as  are  adapted  by  their  properties  to 
the  conditions  of  organic  life  on  the  third  planet  of 
the  solar  system,  and  it  is  certainly  possible  that 
some  different  scheme  of  organic  life  may  be  sus- 
tained on  Mercury  or  Uranus,  in  which  elements 
rare  to  us  take  the  place  of  oxygen,  nitrogen,  hydro- 
gen, and  carbon,  and  perhaps  also  the  elements 
missing  in  our  classification  may  be  found  in  some 
other  world,  revolving  around  Sirius  or  Arcturus, 
where  oxygen,  sulphur,  and  iron  may  be  among  the 
rarities  of  science. 

All  this  is,  of  course,  the  purest  hypothesis,  and 
such  speculation  can  lead  to  no  positive  results ;  but 
the  very  possibility  of  such  speculations  as  those 
in  which  we  have  been  indulging  in  this  connec- 
tion illustrates  most  pointedly  the  great  truth  I 
am  endeavoring  to  enforce.  The  thought  em- 
bodied in  the  scheme  of  chemical  elements  is 
something  entirely  apart  from  their  material  forms, 
and  the  moment  this  thought  is  apprehended  by 
man,  it  opens  to  his  imagination  vistas  of  possible 
realities  which  entirely  transcend  all  human  ex- 
perience. 


286  ILLUSTRATED   IN  ASTRONOMY. 

If  next  we  compare,  more  carefully  than  before, 
the  periods  of  revolution  of  the  planets  around  the 
Sun,  we  shall  find  that  the  same  general  principle 
holds  true.  The  observed  periods,  you  will  notice 
by  the  table  on  page  272,  do  not  exactly  correspond 
to  the  simple  ratios  which  express  the  law,  and  the 
same  is  true  of  the  distribution  of  leaves  around  the 
stem  of  a  plant,  and  in  fact  of  all  classes  of  phenom- 
ena in  nature.  In  each  we  observe  only  a  tendency 
towards  a  maximum  effect,  which  is  the  perfect 
expression  of  the  law,  but  which  is  seldom  fully 
reached.  The  limits  of  variation  are  broader  in 
some  cases  than  in  others,  but  we  find  no  case  in 
which  the  accordance  is  absolute. 

In  none,  however,  of  the  purely  physical  laws  is 
this  character  so  strongly  marked  as  in  the  structure 
of  animals  and  plants.  It  is  well  known  that  all 
organized  forms,  although  so  wonderfully  diversi-* 
fied,  are  fashioned  after  a  few  general  types.  In  the 
animal  kingdom  there  are  only  four  general  plans, 
represented  by  the  Radiata,  the  Mollusca,  the  Arti- 
culata,  and  the  Vertebrata,  and  all  the  animals  of 
any  one  of  these  great  divisions  are  organized  alike. 
For  example,  in  all  vertebrate  animals  we  find 
essentially  the  same  parts ;  and  similar  homologies, 
as  they  are  called,  may  be  traced  throughout  the 
animal  kingdom,  and  any  anatomist  will  point  out 
to  you  in  the  skeleton  of  a  fish,  of  a  reptile,  of  a 
bird,  or  of  a  quadruped,  the  bones  which  correspond 
to  the  various  parts  in  the  skeleton  of  a  man.  In 
the  wings  of  a  bat  the  bones  of  the  human  arm  may 
readily  be  traced.     Moreover,  very  frequently  when 


ILLUSTRATED   IN  ZOOLOGY.  28/ 

there  is  no  use  for  a  given  organ,  it  is  still  present  in 
a  rudimentary  condition.  Professor  Wyman  found 
rudimentary  eyes  in  the  so-called  eyeless  fishes  of  the 
Mammoth  Cave,  and  equally  striking  examples  of  the 
same  general  truth  are  familiar  to  every  one. 

Here,  then,  is  a  most  obvious  distinction  between 
the  conception  and  the  execution,  and  the  general 
plan  of  the  skeleton  is  preserved,  even  where  there 
is  no  use  for  certain  parts,  and  where  we  might  per- 
haps conceive  of  a  simpler  arrangement  without 
them.  But,  more  than  this,  we  find  that  the  varia- 
tions from  what  we  may  regard  as  the  typical  form 
have  been  obviously  made  in  order  to  adapt  the 
organs  to  certain  specific  ends.  The  same  plan 
which,  developed  in  its  full  perfection,  appears  in 
the  human  hand  and  arm,  reappears,  more  or  less 
fully  carried  out,  in  the  fore  legs  of  a  horse,  in  the 
wings  of  an  eagle,  and  in  the  pectoral  fins  of  a  dol- 
phin ;  and  in  each  case  the  organ  has  been  obviously 
adapted  to  some  special  purpose.  Special  adapta- 
tion has  thus  been  most  beautifully  harmonized  with 
general  law,  and  the  conception  has  been  varied  in 
the  execution  in  order  to  secure  some  wise  and 
important  end. 

We,  of  course,  do  not  forget  that  the  rudimentary 
organs  to  which  we  have  referred  are  looked  upon 
by  the  evolutionists  from  a  very  different  point  of 
view,  and  constantly  cited  as  among  the  strongest 
evidences  cf  the  truth  of  their  theories ;  that  they 
are  regarded  by  them  as  the  survivals  of  a  previous, 
condition  in  which  they  played  their  appropriate 
parts,  and  as  an  inheritance  which  marks  the  ancestry 


288  SURVIVALS  AND  TYPES. 

of  a  species,  as  family  traits  often  mark  the  ancestry 
of  an  individual :  and  although,  as  it  seems  to  us, 
this  explanation  of  the  origin  of  rudimentary  organs 
will  not  hold  in  all  cases,  we  at  once  admit  its  wide 
application,  and  we  leave  all  such  questions  of  proxi- 
mate causes  to  the  naturalists,  to  be  decided  on 
scientific  evidence,  and  on  that  alone.  But  we 
claim  that  the  facts  are  perfectly  consistent  with  the 
operation  of  an  intelligent  first  cause,  and  that  this 
more  comprehensive  interpretation,  so  far  from  ex- 
cluding, includes  all  temporary  influences  and  sub- 
ordinate effects. 

This  subject  is  capable  of  almost  indefinite  illus- 
tration, and  the  vegetable  kingdom  is  as  rich  in  ex- 
amples of  the  principle  we  have  been  discussing  as 
the  animal.  I  have  not,  however,  time  for  further 
details.  The  whole  ground  has  been  most  carefully 
surveyed  by  McCosh  and  Dickie  in  their  excellent 
work  entitled  ^*  Typical  Forms  and  Special  Ends  in 
Creation,"  and  to  this  I  would  refer  those  who  may 
be  interested  to  pursue  the  study  of  these  singular 
facts.  Sufficient,  I  trust,  has  already  been  said  to 
show  that  the  phenomena  of  nature  and  the  results 
of  human  thought  resemble  each  other  in  their  very 
incompleteness. 

While,  therefore,  a  more  careful  study  has  tended 
to  confirm  the  result  at  which  we  arrived  in  the  last 
chapter,  and  has  strengthened  the  impression  that 
the  universe  was  created  by  an  intelligence  like  our 
own,  we  have  also  found  that  the  analogies  of  nature 
point  with  equal  distinctness  to  the  conclusion  that 
this  intelligence  is  a  being  entirely  apart  from  and 


MANIFESTATION   OF  INTELLEGENCE.  289 

infinitely  superior  to  the  matter  he  created  or  the 
laws  he  ordained.  If  these  analogies  are  worth  any- 
thing, they  point  not  to  a  spirit  of  the  universe, 
pervading  and  energizing  matter,  but  they  prove 
the  existence  of  a  personal  God  ;  one  who  can  sus- 
tain to  us  the  relations  of  Father,  Saviour,  and 
Sanctifier;  one  whom  we  can  love,  worship,  and 
adore. 

But  it  may  be  urged  that  I  have  drawn  my  illus- 
trations wholly  from  the  phenomenal  laws  of  nature, 
and  entirely  overlooked  the  great  dynamical  laws, 
which,  like  the  law  of  gravitation,  are  more  precise. 
Moreover,  it  will  be  said  that  the  history  of  astron- 
omy gives  us  every  reason  to  believe  that  these  very 
variations,  to  which  I  have  assigned  such  importance, 
are  merely  necessary  consequences  of  some  higher 
law  not  yet  discovered,  just  as  the  perturbations  of 
the  planetary  orbits  are  the  legitimate  results  of  the 
very  law  they  seemed  at  first  to  invalidate.  I  have 
no  doubt  that  in  part,  at  least,  this  will  be  found  to 
be  the  case.  But  even  in  regard  to  the  law  of  gravi- 
tation, there  always  have  been  residual  phenomena, 
unexplained  by  the  law,  and  so  probably  there 
always  will  be,  until,  as  we  go  on  widening  our  gen- 
eralizations, the  last  generalization  of  all  brings  us 
into  the  presence  of  that  First  Cause  through  whom 
and  by  whom  all  things  are  sustained. 

I  trust  that  the  striking  analogies  between  the 
phenomena  of  nature  and  the  results  of  human 
thought,  which  I  have  been  able  so  imperfectly  to 
illustrate,  have  impressed  you,  as  they  impress  me, 
with  the  profound  conviction  that  the  order  of  nature 
13 


290  ASPECT   OF  NATURE. 

is  the  manifestation  of  an  Infinite  Intelligence,  but 
of  an  Intelligence  apart  from,  and  superior  to,  the 
cosmos  which  it  once  created  and  now  upholds.  If 
I  have  failed  in  my  object,  it  is  because  I  have  been 
unable  to  bring  home  these  analogies  to  your  under- 
standing. The  resemblances  are  so  striking,  that  I 
do  not  believe  a  mind  which  is  conversant  with  the 
facts,  and  unbiassed  by  the  prejudices  of  philosophy 
or  of  education,  can  resist  the  conclusion  that  this 
scheme  of  nature  is  the  manifestation  of  an  intelli- 
gence like  our  own,  at  least  so  far  as  the  Infinite  can 
be  said  to  resemble  the  finite.  Men  may  reasonably 
entertain  differences  of  opinion  in  regard  to  the 
mode  of  action  of  that  Being  who  has  created  the 
universe.  They  may  believe  that  a  certain  amount 
of  power,  together  with  the  germ  of  all  future  exist- 
ence, was  implanted  in  the  original  chaos,  and  that 
the  Deity  has  never  interfered  with  the  natural  action 
and  the  unfolding  of  the  causes  which  He  has  thus 
ordained  ;  but  whatever  theories  of  cosmogony  may 
be  entertained,  short  of  absolute  materiahsm,  he 
must  be  indeed  blinded  by  his  prejudices  who  refuses 
to  recognize  in  these  analogies  the  evidence  of  intel- 
ligence and  thought. 

I  do  not,  of  course,  regard  analogies  as  proofs,  nor 
do  I  believe  that  this  argument  from  general  plan 
could  supply  the  place  of  the  great  argument  from 
Design.  The  last  lies  at  the  basis  of  Natural  The- 
ology, and  all  the  rest  is  merely  subsidiary  to  the 
great  central  light.  Moreover,  while  the  argument 
from  design  comes  home  to  every  man*s  understand- 
ing, these  analogies  appeal  with  their  full  force  only 


HUMAN  SYMPATHY  WITH   NATURE.  2gi 

to  the  few  who  are  able  to  study  the  processes  of 
nature  for  themselves,  as  they  alone  are  familiar 
with  the  phenomena  in  which  the  resemblances  are 
seen.  But  to  the  student,  whose  life  has  been  passed 
in  successful  investigation,  and  whose  soul  has  been 
brought  into  sympathy  with  the  harmonies  of  nature, 
these  tokens  are  constantly  assuring  him  of  the  pres- 
ence of  his  God.  Every  discoverer  feels — when  in 
brought  face  to  face  with  a  great  truth,  he  cannot 
resist  the  feeling — that,  in  discovering  a  law,  he  has 
been  brought  nearer,  not  to  a  blind  agency,  but  to 
Omnipotence  itself.  To  this  conclusion  he  is  not  led 
solely  by  philosophy ;  for  although  he  may  defend 
his  conviction  on  reasonable  grounds,  in  its  full  power 
it  transcends  all  human  philosophy.  Man  cannot 
always  tell  why  he  knows.  But  when  illuminated 
from  the  altar  of  his  faith,  all  nature  wears  a  new 
aspect,  and  his  spiritual  eye  discovers  everywhere 
acting  that  same  Infinite  Intelligence  which  "spake 
in  time  past  unto  the  fathers  by  the  prophets,"  and 
'*  hath  in  these  last  days  spoken  unto  us  by  his 
Son." 

Do  I  hear  it  said  that  such  loose  reasoning  is  a  gross 
violation  of  the  Baconian  philosophy,  and  of  that 
severe  induction  by  which  alone  science  has  been 
built  up  ?  But  do  we  not  know,  have  we  not  seen, 
that  the  whole  structure  of  science  rests  on  no  firmer 
foundation  than  these  very  analogies  of  nature, — 
that  at  the  beginning  of  all  knowledge,  where  we 
should  most  expect  infallibility,  we  find  only  uncer- 
tainty and  doubt  ? 

Science  is  a  grand  temple  built  by  man  to  glorify 


292  SCIENCE   RESTS   ON   FAITH. 

his  Maker,  its  unfinished  spire  pointing  to  heaven, 
but  its  foundations  resting  on  a  cloud.  The  work 
has  been  done  as  well  as  faithful  hearts  and  active 
hands  could  do  it.  Examine  its  walls  and  its  but- 
tresses, and  from  base-stone  to  coping  you  will  find 
no  defect.  Each  block  has  been  so  carefully  wrought 
and  so  firmly  clamped  in  its  place,  with  all  the 
strength  of  iron  logic,  that  you  will  unhesitatingly 
conclude  that  the  mighty  structure  has  been  reared, 
not  for  time,  but  for  eternity.  Yet  it  all  rests  on  a 
cloud.  Let  that  cloud  be  dispersed,  and  only  God 
can  tell  whether  the  structure  shall  stand  or  fall. 

Are  we  then,  you  will  ask,  to  mistrust  these 
boasted  results  of  science  ?  Is  this  imposing  struc- 
ture all  a  phantom,  a  mere  day-dream,  from  which 
we  shall  awake  on  the  morning  of  eternity  to  find  all 
passed  ?  Certainly  not !  God  has  not  endowed  his 
creature  with  faculties  of  observation  merely  to 
delude  him,  and  with  an  intellect  solely  to  lead  him 
into  error.  He  has  not  raised  up  the  long  line  of 
scientific  heroes  of  every  age,  merely  to  deceive 
themselves  and  mislead  the  world.  No  !  the  temple 
of  science  will  stand  fast.  That  cloud  on  which  it 
rests  is  a  firmer  foundation  than  any  granite  rock ; 
for  it  is  not  of  man,  but  of  God.  Yet  let  us  not  for- 
get that  this  assurance  is  based  only  on  the  same 
faith  which  is  the  "  substance  of  things  hoped  for, 
the  evidence  of  things  not  seen." 

*'  We  have  but  faith  :  we  cannot  know  ; 
For  knowledge  is  of  things  we  see  ; 
And  yet  we  trust  it  comes  from  Thee, 
A  beam  in  darkness  :  let  it  grow." 


CHAPTER  X. 

NECESSARY  LIMITATIONS  OF  SCIENTIFIC  AND  RE- 
LIGIOUS THOUGHT. 

I  HAVE  endeavored  to  show  that  the  evidence 
which  all  nature  affords  of  a  personal  God  is 
wholly  independent  of  the  theories  of  cosmogony 
we  may  assume.  But  although  our  doctrine  of 
causation  may  not  impair  the  evidence  of  an  origi- 
nal design,  it  is  not  so  with  the  other  bearings  of 
the  subject.  For  if  nature  be  a  mere  machine, 
weaving  the  complex  web  of  destiny  with  the  same 
precision  and  certainty  with  which  a  carpet-loom 
weaves  the  pattern  of  a  carpet,  then  the  Christian's 
idea  of  a  superintending  Providence  cannot  be  true. 
If  nature  has  been  evolved  solely  under  necessary 
conditions  and  laws,  with  which  the  Creator  has 
never  interfered  since  he  wound  up  the  immense 
weight  which  set  the  whole  in  motion  and  still  main- 
tains the  preordained  beats  of  the  great  pendulum 
of  the  universe, — if  with  an  archangel's  intellect  we 
could  predict  every  event  in  nature  with  the  same 
certainty  with  which  we  now  foretell  the  phases  of 
an  eclipse, — then  I  say  again  that  the  visions  of  an 
overshadowing  Providence  which  have  appeared  to 

293 


294  SUPERINTENDING  PROVIDENCE. 

US  at  those  milestones  on  our  life's  journey  where, 
wearied  and  disheartened,  we  have  sat  down  to  rest, 
are  nothing  but  a  delusion  and  a  dream.  It  does 
not  remove  the  difficulty  here  referred  to,  to  say  that 
our  lives  are  parts  of  this  preordained  plan,  or  even 
to  admit  that  God  may  interfere  in  the  moral  world 
by  influencing  the  will  of  man;  for  every  one  is  con- 
scious that  his  will  has  not  been  thus  directly  influ- 
enced, and  knows,  moreover,  that  the  circumstances 
of  his  condition  have  always  concealed,  at  the  time, 
the  kind  Providence  by  which  he  has  been  led. 
And  when  your  theory  leads  to  this,  that  man  has 
been  put  into  a  world  of  probation  and  trial,  and 
there  left  to  walk  over  pitfalls  with  his  eyes  blinded, 
every  unsophisticated  mind  will  feel — say  what  you 
will — that  the  character  of  the  God  you  worship  is 
more  truly  symbolized  by  the  car  of  Juggernaut  than 
by  the  cross. 

A  great  deal  of  false  prejudice  against  scientific 
study  arises  from  a  mistaken  impression  that  the 
materialist's  interpretation  of  nature  is  the  natural 
and  necessary  result  of  all  scientific  thought. 
Hence  not  a  few  religious  minds  have  concluded 
that  the  methods  of  science  must  be  all  wrong,  and 
its  conclusions  wholly  untrustworthy.  It  will  not, 
therefore,  be  out  of  place  in  this  connection  to  con- 
sider briefly  whether  the  materialist's  idea  of  causa- 
tion is  the  necessary,  or  even^the  probable  conclu- 
sion to  which  the  observed  facts  of  nature  and  the 
legitimate  methods  of  science  lead.  We  must  re- 
member, however,  while  discussing  this  subject,  that 
we  have  passed  the  limits  of  human  knowledge,  and 


IDEA   OF   FORCE.  295 

cannot  therefore  expect  by  our  unaided  processes  of 
thought  to  prove  or  disprove  anything.  We  cannot 
determine  absolutely  whether  the  materialist's  theory 
be  true  or  false  ;  for  science  has  not  the  knowledge 
which  would  enable  it  to  form  a  decision.  The  only 
question  for  us  is,  whether  this  theory  is  the  neces- 
sary theory,  or  even  the  most  probable  theory  ;  and 
if  it  is  not  either  the  one  or  the  other,  then  the 
theory  is  of  no  weight.  One  man's  theory  is  as  good 
as  another's,  provided  both  are  equally  consistent 
with  facts.  If,  then,  we  can  show,  on  scientific 
grounds  alone,  that  the  Christian's  theory  of  causa- 
tion is  as  probable  as  the  materialist's,  we  shall  in 
regard  to  this  point  also  fully  sustain  the  position 
we  have  taken  in  regard  to  scientific  studies.  Surely 
science  is  no  more  responsible  for  the  excesses  of 
theorists  than  is  religion  for  the  crimes  of  bigots, 
and  it  should  be  sufficient  to  satisfy  any  religious 
mind,  that  there  is  a  Christian  theory  which  is  per- 
fectly consistent  with  all  known  facts. 

It  is  easy  to  understand  the  relative  position  of 
the  two  theories  of  causation  after  we  have  become 
acquainted  with  the  facts  which  both  must  neces- 
sarily explain.  Let  us  review,  then,  very  briefly, 
these  facts,  which  are  more  or  less  familiar  to  every 
one.  An  innate  principle  of  the  human  mind  com- 
pels us  to  believe  that  every  change  must  have 
an  adequate  cause,  and  leads  us  to  refer  the  phe- 
nomena of  nature  to  what  we  call  forces.  Thus  the 
falling  of  an  avalanche,  the  flowing  of  the  tides,  the 
beating  of  the  waves,  the  blowing  of  the  winds,  the 
crashing  of  the  lightning,  the  burning  of  the   fire, 


296  IDEA  OF  FORCE. 


the  moving  power  of  steam,  and  the  impression  of 
light,  must  all  have  an  adequate  cause,  and  to  this 
cause  we  give  the  name  oi  force.  We  use  this  word 
so  frequently  and  so  familiarly  that  we  are  apt  to 
think  that  we  associate  with  it  a  definite  conception  ; 
but  a  moment's  reflection  will  show  that  in  regard 
to  the  nature  or  origin  of  force  we  have  no  absolute 
knowledge.  This  word  is  merely  our  name  for  the 
unknown  cause  of  natural  phenomena.  The  unedu- 
cated mind  naturally  refers  the  origin  of  all  force  to 
the  bodies  from  which  it  appears  to  emanate,  and 
regards  it  either  as  a  quality  inherent  in  matter,  as 
in  the  phenomena  of  gravitation,  or  as  a  property 
superimposed  upon  matter,  as  in  the  phenomena  of 
light,  heat,  magnetism,  and  electricity.  In  either 
case,  however,  it  is  regarded  as  a  quality  of  matter. 
Moreover,  the  uneducated  mind,  impressed  most  of 
all  by  the  great  diversity  in  physical  phenomena, 
naturally  infers  that  a  similar  diversity  exists  in  the 
forces  which  produce  them,  and  thus  is  led  to  the 
idea  that  there  are  different  kinds  of  force.  Hence 
men  have  been  led  to  refer  the  falling  of  bodies  to- 
wards the  earth  to  a  distinct  force  called  gravitatioit, 
the  motion  of  a  steam-engine  to  another  force  called 
heat,  the  burning  of  a  candle  to  a  third  force  called 
chemical  affinity,  and  in  like  manner  to  each  class  of 
phenomena  they  have  assigned  a  peculiar  and  sepa- 
rate force. 

Such  ideas  as  these  are  natural  in  the  infancy  of 
knowledge,  and  we  must  remember  that,  with  all  our 
boast  of  progress,  the  human  race,  so  far  at  least  as 
physical  science  is  concerned,  is  yet  in  its  childhood. 


IDEA  OF   FORCE.  29/ 


The  law  of  gravitation  was  discovered  only  two 
centuries  ago,  and  almost  the  whole  of  the  present 
sciences  of  chemistry  and  physics  has  been  developed 
within  the  lifetime  of  men  now  living.  Many  of  the 
present  generation  were  educated  in  those  very 
natural,  but  crude  notions,  and  it  is  not  until  a  com- 
paratively recent  period  that  even  scientific  men 
have  been  persuaded  that  these  primitive  ideas  must 
be  wholly  abandoned,  or  at  least  radically  modified. 
We  are  now  in  a  transition  stage,  and  hence  arises  a 
great  difficulty  in  discussing  the  subject.  The  lan- 
guage even  of  modern  science  is  based  upon  the 
old  ideas,  and  we  cannot  describe  natural  phenom- 
ena without  using  terms  which  imply  what  almost 
all  thinkers  now  believe  to  be  erroneous  notions. 
Hence,  when  we  attempt  to  present  spiritual  views 
of  the  origin  and  nature  of  force,  we  are  obliged  to 
use  terms  which  imply  the  opposite,  and  our  very 
language  appears  to  condemn  us,  or  at  least  preju- 
dices our  theory.  This  is  especially  true  of  the  word 
force  itself,  and  we  must  carefully  bear  in  mind  that 
the  origin  of  phenomena  is  not  explained  because,  in 
the  language  of  science,  they  have  been  referred  to 
an  assumed  force  with  a  high-sounding  name.  Names 
are  not  things,  and  we  know  nothing  more  of  the 
cause  which  brings  the  apple  to  the  ground  because 
Newton  has  called  it  the  force  of  gravitation,  than 
we  did  before.  He  gave  us  the  law  of  the  motion, 
and  enabled  us  to  predict  how  every  apple  would 
fall,  and  how  every  planet  would  move  throughout 
space,  but  the  cause  of  the  motion  is  as  closely  hid- 
den as  ever.  In  regard  to  the  law  of  gravitation  we 
13* 


298  TRANSFER  OF  ENERGY. 

know  a  great  deal ;  but  in  regard  to  the  force  of 
gravitation — whatever  we  may  think  or  believe  about 
it — we  know  absolutely  nothing,  and  the  same  is  true 
of  every  other  force. 

The  most  remarkable  feature  of  modern  science 
has  been  the  constant  tendency  of  all  investigations, 
during  the  last  fifty  years,  to  show  that  the  same 
energy,  if  only  differently  applied,  may  produce  the 
most  diversified  phenomena;  and  now  almost  all 
the  so-called  forces  of  the  old  philosophy  appear  to 
be  mutually  convertible.  Thus — to  begin  with  a 
lump  of  coal — as  we  have  seen,  a  certain  amount  of 
latent  energy  resides  in  that  black  mass,  which  has 
been  called  the  force  of  chemical  affinity.  Burn  the 
coal, — that  is,  combine  it  with  oxygen, — and  the 
affinity  is  satisfied,  but  the  energy  reappears  as  light 
and  heat.  If  the  coal  is  burnt  under  a  steam-boiler, 
the  heat  expands  the  water  and  converts  it  into 
vapor,  and  then  we  find  the  energy  again  in  the  ex- 
pansive force  of  steam.  The  steam  expands  against 
the  piston  of  the  locomotive,  and  the  energy  passes 
into  the  moving  train.  The  rapidly  moving  mass, 
in  forcing  its  way  through  the  air  and  over  the  iron 
track,  is  constantly  losing  its  moving  power  in  con- 
sequence of  the  friction  it  encounters  ;  but  the  energy 
is  not  lost,  and  if  we  could  follow  it,  we  should  find 
it  reappearing  somewhere  as  heat.  Suddenly  the 
engineer  opens  a  valve,  and  a  portion  of  the  energy 
of  the  steam  gives  motion  to  the  air,  and  the  effect 
is  a  shrill  whistle.  The  brakeman  applies  the  brakes, 
and  the  train  after  a  few  moments  comes  to  rest. 
Its  moving  power  is  gone,  but  the  energy  is  not  lost. 


TRANSFER  OF  ENERGY.  299 

The  motion  has  been  transformed  into  heat,  and  the 
smoking  brake  shows  where  the  energy  has  gone. 

Return  now  again  to  the  lump  of  coal,  and,  in- 
stead of  burning  it  under  a  steam-boiler,  heat  it 
in  a  properly  constructed  furnace  in  contact  with 
roasted  zinc  ore.  This  ore  is  a  compound  of  zinc 
and  oxygen.  The  coal,  in  order  to  satisfy  its  in- 
tense affinity,  seizes  on  the  oxygen  and  sets  the  zinc 
free.  But  although  the  chemical  affinity  of  the  coal 
has  been  satisfied,  no  power  has  been  lost ;  for  the 
energy  which  was  before  latent  in  the  carbon  is 
now  latent  in  the  zinc.  Dissolve  the  zinc  in  dilute 
sulphuric  acid,  and  the  chemical  affinity  of  the  zinc 
will  be  satisfied,  and,  if  certain  conditions  are  ful- 
filled, the  energy  will  take  the  form  of  a  current  of 
electricity.  Cause  this  current  to  flow  through  a 
platinum  wire,  and  this  energy  will  appear  in  the 
heat  and  light  radiated  from  the  glowing  metal. 
Cause  the  same  current  to  flow  in  spiral  lines  around 
a  bar  of  iron,  and  we  find  the  energy  again  in  the 
attractive  force  of  an  electro-magnet.  Connect  with 
the  electro-magnet  appropriate  machinery,  and  the 
same  energy  may  be  so  applied  that  it  will  move  a 
light  boat  or  turn  a  small  lathe.  Lastly,  connect 
with  the  dissolving  zinc  four  thousand  miles  of  iron 
wire,  and  the  energy  will  be  transmitted  across  a 
continent  with  the  velocity  of  thought,  and  write  in 
a  distant  city  the  message  which  it  carries. 

Illustrations  like  these  might  be  multiplied  indefi- 
nitely ;  but  enough,  I  think,  has  been  said  to  show 
that,  to  all  appearance  at  least,  the  same  energy 
may   be   transferred   from  one  mass  of  matter  to 


300  -POTENTIAL  AND  ACTIVE   ENERGY. 

another,  and  that  thus,  while  nothing  but  the  mode 
of  application  has  been  changed,  the  power  may  re- 
appear under  entirely  different  manifestations,  and 
produce  phenomena  wholly  unlike  those  in  which  it 
was  but  a  moment  before  the  active  cause.  The 
truth  of  this  principle  becomes  still  more  evident 
when  we  apply  in  our  experiments  exact  measure- 
ments;  for  we  find  that  in  all  these  transfers  of 
energy  from  mass  to  mass  the  power  reappears 
undiminished.  It  may  remain  latent  for  a  time,  as 
in  a  mass  of  coal,  but  sooner  or  later  it  will  reappear 
without  having  undergone  the  slightest  loss. 

We  must  here  dwell  for  a  moment  upon  an  im- 
portant distinction,  which  has  already  been  implied, 
between  latent  and  active  energy.  It  is  a  distinction 
with  which  every  one  is  practically  familiar,  and  it 
may  therefore  be  made  clear  by  referring  to  a  few 
examples.  A  weight  falling  to  the  ground  from  a 
i  given  height  is  an  example  of  active  energy,  while 
an  equal  weight  suspended  at  the  same  height  rep- 
resents an  equivalent  amount  of  latent  energy.  In 
winding  up  a  clock,  muscular  energy  becomes  latent 
in  the  suspended  weight,  but  reappears  in  mechanical 
motion  as  the  clock  runs  down.  So  also  a  lump  of 
coal,  as  already  stated,  represents  a  certain  amount 
of  latent  energy.  When  the  coal  burns,  its  energy 
becomes  active,  and  takes  the  form  of  heat.  Again, 
in  smelting  zinc  ore  there  is  transferred  to  the  pro- 
duct a  portion  of  the  latent  energy  of  the  coal  used 
in  the  furnace  ;  and  if  in  a  voltaic  battery  the  result- 
ing zinc  dissolves  in  sulphuric  acid,  this  energy 
becomes  active,  and  reappears  in  a  current  of  elec- 


ENERGY  NEVER   LOST.  30I 

tricity.  Some  persons  do  not  like  the  term  latent 
energy,  and  speak  of  energy  which  is  not  in  action 
as  possible  or  potential.  In  like  manner  they  speak 
of  energy  in  action  as  actual  or  kinetic.  But  terms 
are  of  no  importance,  if  only  the  ideas  which  they 
express  are  fully  understood. 

Keeping  this  distinction  in  view,  we  shall  better 
understand  the  bearings  of  the  important  principles 
just  before  stated.  When  energy,  in  passing  from 
one  body  to  another,  changes  its  mode  of  manifesta- 
tion, it  seldom  flows  wholly  into  one  channel,  and 
almost  invariably  more  or  less  of  it  becomes  latent. 
Thus — to  go  back  to  the  example  of  the  steam- 
engine — of  the  energy,  which  is  latent  in  the  coal 
and  becomes  active  in  the  form  of  heat  when  the 
coal  burns,  not  more  than  one-tenth,  at  the  most, 
produces  any  useful  mechanical  effect.  The  rest 
becomes  again  latent  in  changing  the  water  into 
steam,  and  in  heating  and  expanding  the  iron,  the 
bricks,  the  water,  and  the  air  in  contact  with  which 
the  fuel  burns.  All  this  heated  matter  represents  a 
large  amount  of  latent  energy.  It  is  in  the  condi- 
tion of  the  wound-up  weight  of  a  clock,  and,  as  it 
cools,  this  energy  is  distributed  to  surrounding 
bodies.  Were  it  possible,  at  a  given  instant  after 
the  burning  of  the  coal,  to  sum  up  all  the  energy, 
both  active  and  latent,  which  could  be  traced  di- 
rectly back  to  the  burning  fuel,  it  would  be  found 
that  not  the  smallest  fraction  of  the  energy  origi- 
nally in  the  mass  of  coal  had  been  lost.  In  this 
case,  of  course,  accurate  experiments  are  out  of  the 
question ;  but  wherever  it  has  been  possible  to  apply 


302  CONSERVATION   OF  ENERGY. 

measurements,  it  has  been  found  that  the  principle 
here  illustrated  holds  true.  I  should  not  be  able  to 
make  the  methods  of  such  investigations  intelligible 
without  occupying  a  great  deal  of  time.  Let  it  then 
be  sufficient  to  state,  that  all  those  who  have  most 
carefully  studied  the  subject  have  arrived  at  the 
same  results.  There  is,  therefore,  every  reason  to  be- 
lieve that  the  principle  we  have  been  illustrating  is 
universally  true.  Let  us  then  embody  it  in  a  definite 
statement.  All  natural  phenomena  are  the  manifes- 
tation  of  the  same  omnipresent  energy,  which  is  trans- 
f erred  from  07ie  portion  of  matter  to  another  without 
loss. 

But  if  the  principle  as  thus  stated  be  accepted,  we 
cannot  rest  here ;  for  it  involves  this  further  conclu- 
sion, which,  however  marvellous,  must  be  true.  The 
sum.  total  of  all  the  active  and  latent  energies  in  the 
universe  is  cojistant  a?id  invariable.  In  other  words, 
power  is  as  indestructible  as  matter.^ 

This  grand  truth  is  generally  called  the  law  of 
conservation  of  energy,  and,  if  it  cannot  as  yet  be 
regarded  as  absolutely  verified,  there  can  be  no 
question  that  it  stands  on  a  better  basis  to-day  than 
did  the  law  of  gravitation  one  hundred  years  ago. 

But  how  can  I  give  you  any  conception  of  the 
sublimity  of  the  truth  which  this  formal  language  im- 
plies, but  which  no  language  is  adequate  to  express? 
Even  poetry,  in  the  highest  flights  of  fancy,  has 
never  seen  such  a  vision  as  these  vistas  of  actual 

*  Many  philosophers  believe,  with  Newton,  that  matter  in  its  es- 
sence is  only  a  manifestation  of  power,  and  if  so  the  conservation  of 
mass  in  nature  is  only  a  phase  of  the  conservation  of  energy. 


CONSERVATION   OF   ENERGY.  303 

realities  open  to  the  intellect  and  imagination  of 
man.  Review  in  the  light  of  this  grand  generali- 
zation the  subsidiary  truth  which  from  time  to 
time  I  have  endeavored  to  illustrate  in  this  work, 
— namely,  that  all  terrestrial  energy  comes  from 
the  sun.  The  accumulated  power  of  the  sun's  deli- 
cate rays  produces,  as  we  before  saw,  every  mo- 
tion and  every  change  which  takes  place  on  the 
surface  of  this  planet,  from  the  falling  of  an  ava- 
lanche to  the.  crawling  of  a  worm.  But  that  energy, 
as  we  now  know,  is  not  exhausted  on  the  earth. 
To  use  the  eloquent  language  of  another :  ^^  Our 
world  is  a  halting-place  where  this  energy  is  con- 
ditioned. Here  the  Proteus  works  his  spells ; 
the  selfsame  essence  takes  a  million  shapes  and 
hues,  and  finally  dissolves  into  its  primitive  and 
almost  formless  form.  The  sun  comes  to  us  as  heat ; 
he  quits  us  as  heat ;  and  between  his  entrance  and 
departure  the  multiform  powers  of  our  globe  appear. 
They  are  all  special  forms  of  solar  power, — the 
moulds  into  which  his  strength  is  temporarily 
poured,  in  passing  from  its  source  through  infini- 
tude." ^ 

Attempt  now  to  bring  together  in  imagination  all 
the  energies  acting  at  one  moment  on  the  earth,  and 
unite  them  in  one  tremendous  aggregate.  Begin 
with  the  moving  power  of  the  air,  the  hurricanes, 
the  tornadoes,  the  storms,  and  the  gentler  winds 
which  are  everywhere  at  work  from  the  Arctic  to  the 
Antarctic  Pole,  omitting  in  making  the  estimate,  if 

*  Professor  John  Tyndall,  in  the  work  already  quoted,  "Heat 
considered  as  a  Mode  of  Motion." 


304  SOURCE   OF  ENERGY. 

you  choose,  the  Hghtning  and  the  thunder,  which, 
though  brilliant  and  noisy  demonstrations  of  power, 
would  hardly  increase  by  a  unit  the  vast  sum.  Add 
to  this  the  mechanical  power  in  the  mighty  flow  of 
waters,  the  ocean  currents,  the  rivers,  the  cataracts, 
the  glacier-streams,  and  the  avalanches,  all  over  the 
globe.  Bring  into  the  calculation  the  forces  at  work 
in  the  various  phases  of  animal  and  vegetable  life. 
Remember  the  conflagrations,  the  furnaces,  the  fires, 
and  the  other  manifestations  of  the  terrible  energies 
of  the  atmospheric  oxygen,  whenever  it  is  aroused. 
Do  not  even  forget  the  comparatively  insignificant 
power  which  man  is  wielding  with  the  aid  of  powder 
and  of  steam.  Making  now  an  immense  allowance 
for  what  you  must  have  overlooked,  sum  this  all  up, 
— if  you  can  without  bewilderment, — and  what  part 
is  it  of  the  whole  ?  Why,  it  has  been  calculated 
that  it  is  equal  to  but  one  2,300,000,000th  of  the 
force  which  the  sun  is  every  moment  pouring  into 
space.  And  what  is  the  sun?  A  small  star  in  the 
infinitude  of  space,  where  shine  Sirius  and  Arcturus, 
Regulus  and  Aldebaran,  Procyon  and  Capella,  with 
unnumbered  others,  all  shedding  forth  a  far  mightier 
effluence  than  our  feeble  star :  yet  the  grand  total 
of  the  powers  streaming  from  all  the  suns  which 
human  eye  has  seen,  or  which  still  lie  undiscovered 
in  the  depths  of  space,  alone  represents  the  active 
energy  of  the  universe.  My  friends,  there  are  two 
theories  of  causation.  One  regards  this  energy  as 
an  unintelligent  power.  The  other  sees  in  it  simply 
the  will  of  the  Almighty.  They  are  both  theories. 
We  cannot  substantiate  either.     But  which  do  you 


i 


ENERGY  APPEARS  AS   MOTION.  305 

think  is  the  more  probable?  Let  us  not  pass  hasty 
judgment,  but  soberly  weigh  all  the  testimony,  and 
base  our  decision  on  the  best  scientifie  evidence  we 
can  obtain,  and  on  that  alone. 

Thus  far  in  our  discussion  we  have  been  dealing 
with  facts  and  principles  which  every  theory  of 
causation  must  explain.  But  we  now  pass  into 
what  is  rather  the  region  of  speculation,  and  we 
must  step  more  cautiously.  I  have  used  thus  far  the 
terms  ^;^^r^and  transfer  of  energy  ^v^WhowX.  expect- 
ing that  you  would  attach  to  them  any  more  definite 
meaning  than  that  which  is  conveyed  by  the  words 
in  their  most  familiar  use.  Energy  is  a  definite 
thing,  which  is  as  palpable  to  our  senses  as  matter, 
and  which,  in  most  cases  at  least,  we  can  measure 
as  accurately.  Any  one  who  has  been  stunned  by 
a  blow,  bruised  by  a  fall,  burnt  by  a  fire,  dazzled 
by  the  sun,  or  paralyzed  by  a  shock  of  electricity, 
knows  well  enough  what  energy  is;  and  the  doc- 
trine of  the  conservation  of  energy  is  wholly  in- 
dependent of  any  theory  which  men  may  entertain 
in  regard  to  its  essence.  For  this  reason,  I  have 
aimed  to  present  the  grand  doctrine  of  modern  sci- 
ence entirely  free  from  all  speculations  whatsoever ; 
but  now  that  we  are  seeking  to  go  behind  the 
external  phenomena,  it  will  be  well  for  us  to  con- 
sider very  briefly  a  theory  which,  although  it  does 
not  profess  to  explain  what  energy  is  in  its  essence, 
nevertheless  may  give  to  the  mind  a  more  definite 
conception  of  its  mode  of  action.  The  theory,  it  is 
true,  cannot  be  regarded  as  fully  established ;  but 
it  represents   the    undoubted   tendency  of  science, 


3o6  MOTION  OF  MOLECULES. 

and  the  materialists  would,  of  all  others,  be  the  first 
to  accept  it.  According  to  the  modern  view,  all  en- 
ergy appears  as  motion,  and  this  too  whether  it  be 
manifested  in  mechanical  work,  or  in  the  more  sub- 
tile phenomena  of  sound,  light,  heat,  chemical  affin- 
nity,  electricity,  or  magnetism.  We  must,  however, 
extend  our  idea  of  motion,  and  not  limit  it,  as  is  usu- 
ally done,  to  the  motion  of  visible  masses  of  matter. 
Even  the  smallest  material  masses  perceptible  to 
our  senses  must  be  regarded  as  aggregates  of  still 
smaller  masses,  which  we  call  molecules.  These 
molecules,  moreover,  even  in  the  densest  bodies, 
cannot  be  in  contact,  and  we  must  picture  them  to 
our  imagination  each  as  a  tiny  world  poised  in  space. 
The  same  relation  which  the  worlds  bear  to  the  cos- 
mos, we  conceive  that  these  molecules  bear  to  the 
microcosmos  which  every  mass  of  matter  represents, 
and  it  is  believed  that  the  motions  of  suns  and  sys- 
tems have  their  miniature  in  the  motions  of  these 
molecules.  The  ether,  also,  of  which  I  spoke  in  the 
second  chapter  as  filling  celestial  space,  is  supposed 
to  pervade  equally  the  molecular  spaces,  to  surround 
each  molecule  with  a  highly  elastic  atmosphere,  and 
to  be  the  medium  by  which  motion  is  transmitted 
throughout  a  universe  which  includes  the  infinitesi- 
mal as  well  as  the  infinite.  Moreover,  we  conceive 
that  the  motion  of  the  molecule  is  the  exact 
counterpart  of  the  motion  of  a  world  or  of  the  mo- 
tion of  a  ball,  and  that  all  motion  obeys  the  selfsame 
laws.  As  when  an  ivory  billiard-ball  strikes  another, 
it  gives  up  the  whole  or  a  part  of  its  motion  to  the 
second  ball,  so  we  believe  that  one  molecule  may 


MOTION  OF  MOLECULES.  307 

transmit  motion  to  another.  In  like  manner,  as  an 
impulse  is  transmitted  through  a  long  line  of  billiard- 
balls,  and  the  last  ball  only  appears  to  move,  so  also 
we  conceive  that  the  electrical  impulse  is  transmitted 
from  molecule  to  molecule  through  the  telegraph 
wire,  and  produces  perceptible  motion  only  when 
transformed  into  magnetism  at  the  end  of  a  thousand 
miles.  Again,  motion  may  be  transmitted  from  mole- 
cules to  masses  of  matter ;  for  although  the  impulse 
imparted  by  a  single  molecule  may  be  as  nothing,  the 
accumulated  effect  of  millions  on  millions  of  these 
impulses  may  be  immense.  In  this  way,  as  we  con- 
ceive, the  motions  of  the  ether  particles  in  the  sun- 
beams unite  to  produce  all  the  grand  phenomena  of 
nature.  On  the  other  hand,  the  motion  of  great 
masses  may  be  suddenly  resolved  into  the  motions 
of  the  molecules  composing  these  masses,  and  thus, 
when  motion  outwardly  appears  to  cease,  it  may 
only  be  transferred  from  the  previously  moving  body 
to  the  molecules  within.  When  the  cannon-balls, 
with  their  immense  velocity,  strike  the  iron-clad  fri- 
gate and  fall  harmlessly  from  her  armor-plates,  the 
particles  of  iron  take  up  the  motion  of  the  ball,  and 
indicate  by  a  higher  temperature  that  the  energy 
has  not  been  lost. 

Understanding,  then,  the  term  motion  in  the  ex- 
tended sense  just  explained,  we  shall  comprehend 
more  clearly  the  theory  stated  above.  This  theory 
supposes  that  the  phenomena  of  sound,  light,  heat, 
and  electricity  are  produced  by  the  motions  of  mole- 
cules, in  the  same  way  that  the  grander  phenomena 
of  mechanics  and  astronomy  are  caused  by  the  mo- 


308  MOTION  OF  MOLECULES. 

tion  of  large  masses  of  matter.  The  transmission 
of  energy  is,  then,  the  direct  result  of  the  transmis- 
sion of  motion,  and  the  conservation  of  energy  is 
fully  explained  by  the  well-known  law  of  inertia, 
which  the  motions  of  all  matter  necessarily  obey.  I 
have  not  time  to  enter  into  any  details  in  regard  to 
the  mode  of  motion  by  which  light,  heat,  and  all  this 
class  of  phenomena  are  produced,  other  than  those 
already  given  in  the  previous  chapters  of  this  book ; 
but  I  take  great  pleasure  in  referring  my  readers  to 
the  work  of  Professor  Tyndall,  already  frequently 
quoted,  as  by  far  the  best  popular  statement  of 
the  subject  that  has  ever  been  made.  Indeed, 
great  differences  of  opinion  in  regard  to  the  mode 
of  the  molecular  motion  are  entertained  by  those 
who  accept  the  theory  in  its  general  statement,  and 
in  many  cases  we  can  form  no  conception  of  the 
peculiar  phase  which  the  motion  assumes.  It  is 
sufficient  for  my  purpose  if  I  have  been  able  to 
make  clear  the  general  principle,  and  I  will  only  add 
a  few  numerical  results,  which  will  show  what  a  pre- 
cise form  the  theory  has  taken  in  the  minds  of 
scientific  men. 

According  to  the  modern  theory,  when  we  heat 
a  body  we  merely  impart  to  its  molecules  a  greater 
velocity  of  motion.  Now,  according  to  the  experi- 
ments of  Professor  Joule,  when  we  raise  the  tem- 
perature of  a  pound  of  water  two  P'ahrenheit  de- 
grees, we  distribute  among  the  molecules  of  the 
liquid  an  amount  of  motion  equal  to  that  acquired 
by  a  weight  of  two  pounds  in  falling  JJl  feet;  and  a 
simple  calculation  will  show  that  this  is  represented 


MOTION   OF   MOLECULES.  309 

by  a  Minle  ball,  weighing  one-eighteenth  of  a  pound, 
moving  with  a  velocity  of  1,338  feet  in  a  second."^ 
The  amount  of  motion,  therefore,  which  is  imparted 
to  the  particles  of  water  in  an  ordinary  tea-kettle 
during  the  process  of  boiling,  must  be  in  the  aggre- 
gate vastly  greater  than  that  ever  acquired  by  any 
projectile.  We  shall  arrive  at  a  still  more  remark- 
able result  if  we  examine  in  the  light  of  our  theory 
the  process  of  chemical  combination  by  which  water 
is  formed.  In  this  process  of  burning,  one  pound 
of  hydrogen  gas  combines  with  eight  pounds  of  oxy- 
gen gas  to  form  nine  pounds  of  water.  Although 
the  distances  which  separate  the  atoms  of  the  two 
gases  before  combination  are  utterly  inapprecia- 
ble by  our  senses,  yet,  in  passing  over  these  dis- 
tances, they  acquire  a  velocity  which  causes  them 
to  clash  together  with  tremendous  energy,  and  in 
the  collision  this  form  of  atomic  motion  is  trans- 
muted into  that  other  mode  of  motion  which  we 
call  heat.  Incredible  as  it  may  appear,  the  amount 
of  motion  which  in  the  act  of  combination  alone  is 
thus  transmuted  into  heat  corresponds  to  the  fall  of 
a  ton  weight  down  a  precipice  22,320  feet  high. 
,Such  illustrations  might  be  multiplied  indefinitely  ; 
but  you  will  see  from  these  how  purely  mechanical 
the  idea  is  which  we  associate  with  the  motion  of  a 
molecule,  and  you  must  have  been  impressed  by 
the  magnitude  of  the  energy  which  these  molecular 
motions  represent.     "  I  have  seen,''  says    Professor 

*  In   making  the  calculation,   it  must  be  remembered    that   the 
amount  of  motion  is  measured  by  the  square  of  the  velocity. 


310  CAUSE   OF   MOTION. 

Tyndall,  "  the  wild  stone  avalanches  of  the  Alps, 
which  smoke  and  thunder  down  the  declivities  with 
a  vehemence  almost  sufficient  to  stun  the  observer. 
I  have  also  seen  snow-flakes  descending  so  softly  as 
not  to  hurt  the  fragile  spangles  of  which  they  were 
composed  ;  yet  to  produce  from  aqueous  vapor  a 
quantity  of  that  tender  material  which  a  child  could 
carry,  demands  an  exertion  of  energy  competent  to 
gather  up  the  shattered  blocks  of  the  largest  stone 
avalanche  I  have  ever  seen,  and  pitch  them  to  twice 
the  height  from  which  they  fell.'*  If  such,  then,  be 
the  measure  of  these  atomic  motions,  we  can  easily 
conceive  how  the  motion  of  the  cannon-ball  might 
be  transferred  to  the  particles  of  the  armor-plate 
without  much  apparent  result,  and  even  how  the 
energy  of  a  world  might  be  maintained  by  the  mo- 
tion of  the  molecules  in  the  sunbeam. 

Accepting,  then,  this  new  theory  of  science,  and 
admitting  that  all  energy  is  manifested  in  motion, 
we  reduce  at  once  our  discussion  of  the  doctrine  of 
causation  to  this  simple  question, — What  is  the 
primary  cause  of  motion  ?  If  we  can  explain  the 
simplest  case  of  motion,  we  have  solved  the  problem 
for  the  universe.  Take,  for  example,  a  boy*s  ball, 
moving  through  the  air  under  the  impulse  of  a  well- 
directed  blow.  Do  we  not  know  something  of  the 
cause  of  that  motion  ?  Is  it  not  connected  with  the 
muscular  contraction  of  the  boy's  arm,  produced  by 
his  will  ?  Is  not  his  volition,  acting  mysteriously  on 
matter,  at  least  the  occasion  of  the  motion?  It  is 
perfectly  true  that  the  will  does  not  create  the  mo- 
tion.    The   ball  is  impelled  by   a  portion  of   that 


THEORY   OF   CAUSATION.  3II 

energy  in  nature  which  man  can  neither  increase  nor 
diminish.  But  still  the  boy's  will  is  the  occasion  of 
the  motion.  It  has  opened  the  channel  through 
which  the  energy  of.  nature  has  flowed  to  produce 
the  specific  result  which  the  boy  desired.  So,  in  a 
thousand  other  ways,  man  is  able  to  come  down,  as 
it  were,  upon  nature,  and  to  introduce  a  new  condi- 
tion into  the  chain  of  causation.  Place  the  point  of 
contact  as  far  back  as  you  please,  theorize  about  the 
subject  as  you  may,  the  fact  still  remains  the  same. 
Our  will  does  act  on  matter,  and  does  act  to  produce 
most  efificient  results.  Here  is  energy  exerted  of 
whose  cause  we  have  the  consciousness  within  our- 
selves, and,  if  the  analogy  is  worth  anything,  it  points 
to  but  one  conclusion,  —  namely,  that  motion  is 
always  the  manifestation  of  will.  As  the  boy's  will 
acted  on  that  particle  of  matter,  which,  though  moved 
perhaps  but  an  atom's  breadth  from  its  position,  set 
in  action — as  if  by  the  touching  of  a  spring — the  train 
of  natural' causes  which  gave  motion  to  the  ball,  so 
we  may  suppose  that  the  Divine  will  acts  in  nature. 
According  to  this  view,  the  energy  which  sustains 
the  universe  is  the  will  of  God,  and  the  law  of  con- 
servation is  only  the  manifestation  of  His  immutable 
being, — '^  the  same  yesterday,  and  to-day,  and  for- 
ever." 

We  do  not  say  that  this  theory  can  be  proved — 
for  certainty  here  is  out  of  the  question — but  we  do 
claim  that  it  is  based  on  the  only  analogy  which 
nature  affords,  that  it  is  a  legitimate  deduction  of 
science,  and  that  it  is  perfectly  consistent  with 
Christian  faith.     On  a  subject  where  science  can  only 


312  RELATIVE  LIMITATIONS. 

grope,  the  wildest  theories  are  possible  ;  but  these 
should  not  trouble  a  well-balanced  mind,  so  long  as 
there  exists  an  equally  probable  theory  which  can 
be  reconciled  with  the  purest  faith.  It  has  been  my 
aim  in  this  chapter  to  show,  not  only  that  such  a 
theory  is  tenable,  but  also  that  the  Christian  theory 
of  causation  is  the  most  probable  theory  of  science  ; 
and  my  earnest  hope  is,  that,  for  some  minds  at 
least,  the  considerations  I  have  offered  will  help  to 
reconcile  the  apparent  conflict  between  science  and 
religion  which  materialism  is  ever  striving  to  foment. 
Allow  me  to  add,  in  concluding,  one  or  two  other 
suggestions  which  may  be  of  value  in  the  same 
direction. 

I  cannot  but  believe  that  the  appearance  of  clash- 
ing between  science  and  religion  would  be  wholly 
avoided,  if  the  teachers  both  of  God's  unwritten  and 
of  His  written  word  would  pay  more  regard  to  the 
necessary  limitations  of  scientific  and  religious 
thought.  On  subjects  where  the  methods  of  ac- 
quiring knowledge  are  so  utterly  unlike,  where  the 
relations  of  knowledge  to  the  human  understanding 
are  so  different,  it  is  in  vain  to  expect  literal  accord- 
ance. Science,  both  in  its  methods  and  its  results, 
addresses  the  understanding  exclusively  ;  Christian- 
ity appeals  chiefly  to  the  heart.  Science  aims  to 
instruct ;  Christianity  aims  to  persuade.  Science  is 
attained  by  study,  and  is  possible  only  for  the  few  ; 
Christianity  is  a  free  gift  from  God  to  all  men  who 
will  receive  His  Son.  The  results  of  science  are 
fully  comprehended,  and  can  be  expressed  in  definite 
terms ;  the  truths  of  Christianity  stand  on  a  level 


METHOD   OF  SCIENCE.  313 

above  man's  intellect,  and  can  only  be  shadowed 
forth  in  types  and  symbols.  The  forms  of  science 
are  constantly  changing ;  the  types  and  symbols  of 
Christianity  are  permanent.  Lastly,  while  the  lan- 
guage of  science  may  be  so  varied  from  time  to  time 
as  to  express  accurately  the  current  ideas,  Christian- 
ity necessarily  retains  the  forms  through  which  it 
w^as  first  revealed.  Under  such  conditions,  how  can 
it  be  expected  that  the  letter  of  revelation  should 
agree  with  the  language  of  science  ?  One  might  as 
reasonably  find  fault  with  nature  because  its  crystals 
are  not  perfect,  as  criticise  the  Bible  because  its 
language,  although  embodying  divine  truth,  is  not 
free  from  the  necessary  limitations  and  imperfec- 
tions of  the  human  medium  of  thought. 

Consider  in  this  connection  the  method  of  science 
which  we  have  already  discussed  at  some  length  in  a 
previous  chapter.  Remember  that  in  nature  we 
observe  only  a  sequence  of  phenomena.  The  idea  of 
a  cause  is  supplied  by  our  own  minds,  and  every 
phenomenon  is  so  surrounded  and  obscured  by  ad- 
ventitious circumstances  that  it  is  frequently  very 
difficult  to  establish  the  causal  connection  with  the 
antecedents.  Science  endeavors  to  discover  this 
connection  by  a  process  of  elimination,  which  it  con- 
ducts in  various  ways.  It  notices,  for  example,  that 
while  certain  antecedents  invariably  accompany  a 
given  effect,  others  are  sometimes  absent,  and  in  this 
way  the  accidental  concomitants  may  be  to  a  greater 
or  less  extent  eliminated.  The  process  of  elimina- 
tion is  more  rapid  and  satisfactory  when  the  phenom- 
enon is  so  far  under  our  control  that  we  can  vary  the 
14 


314  THE   RADIOMETER. 

conditions  by  experiment.  If,  then,  we  find  that  a 
given  condition  may  be  omitted  or  varied  without 
influencing  the  result,  we  can  conclude  with  great 
safety  that  this  antecedent  is  not  essential.  On  the 
other  hand,  if  we  find,  either  from  experiment  or  ob- 
servation, that  the  effect  varies  with  the  condition, 
any  change  in  the  antecedent  being  followed  by  a  cor- 
responding change  in  the  phenomenon  we  are  study- 
ing, then  we  feel  great  confidence  that  we  have  found 
one  at  least  of  the  causes  we  are  seeking.  When  a 
connection  of  this  kind  is  established,  the  effect  is 
said  to  be  a  function  of  its  antecedent,  and  it  is 
frequently  possible  to  express  this  function  by  a 
mathematical  formula,  so  that  we  can  predict  with 
absolute  certainty  the  nature  and  extent  of  the 
effect  which  will  under  any  given  circumstances  be 
produced;  and  in  this  case  our  certainty  in  regard 
to  the  immediate  cause  of  the  phenomenon  is  of 
the  highest  order  which  can  be  reached  in  science. 
An  illustration  will  make  the  point  clearer. 

A  few  years  ago.  Professor  Crookes,  of  London, 
having  observed  that  light  pith  balls  delicately  sus- 
pended in  a  vacuous  tube  were  under  certain  con- 
ditions repelled  by  the  sun's  rays,  was  led  on  from 
step  to  step  until  he  had  constructed  the  instrument 
now  so  well  known  as  the  radiometer,  in  which  a 
delicate  wheel  is  rapidly  turned  by  the  rays  of  the 
sun,  or  by  the  rays  of  any  source  of  bright  light, 
shining  on  its  blackened  vanes. 

At  first  sight  the  effect  seemed  to  be  the  result  of 
a  direct  mechanical  action  of  the  rays  of  light,  and 
this  explanation  was  for  a  time  generally  received. 


THE   RADIOMETER. 


But   it  soon  appeared  that  if  the  he^t-givi^fe/rays'*"/ ,^ 
were  absorbed  by  passing  the  beam  of  light  throt^gh       ^  }- 
a  solution  of  alum,  the  motion  of  the  vanes  was  ar^/  \ . 
rested,  or  at  least  very  greatly  retarded,  while,  on  the       f^i 
other  hand,  when  the  light-giving  rays  were  absorbed 
by  a  solution  of  iodine,  a  medium  which  although  "^ 

opaque  to  light  is  pervious  to  heat,  the  motion  was 
maintained  with  nearly  its  full  activity.  Further,  it 
was  soon  found  that  the  motion  could  be  produced 
by  any  cause  which  determined  a  slight  difference  of 
temperature  between  the  blackened  faces  of  the 
vanes  and  the  surface  of  the  inclosing  glass  bulb,  and 
that  while  the  motion  was  in  one  direction  when 
the  vanes  were  warmer  than  the  glass,  the  motion 
was  in  the  opposite  direction  when  these  conditions 
were  reversed  ;  and  further,  that,  other  things  being 
equal,  the  greater  the  difference  of  temperature  the 
more  rapid  was  the  motion.  Hence,  after  a  long 
series  of  experiments,  it  was  concluded  that  the 
motion  of  the  radiometer  was  an  effect  of  a  differ- 
ence of  temperature  between  its  parts,  or,  in  other 
words,  that  the  radiometer  is,  like  the  steam  engine, 
simply  an  example  of  a  heat  engine.  Thus  Pro- 
fessor Crookes  was  able  to  discover  the  proximate 
cause  of  the  remarkable  phenomenon  he  had  ob- 
served, and  having  done  this  he  had  learned  all  that 
could  be  known  with  certainty  in  regard  to  it. 

This  example  is  a  fair  illustration  of  the  method 
of  science,  and  scientific  ability  is  shown  in  the 
power  of  so  directing  observations  or  making  experi- 
ments as  to  establish  the  true  causal  relations  in 
any  case.     No  one  supposes,  however,  that  having 


3l6  MOLECULAR  THEORY. 

established  this  relation  we  have  discovered  an  "  effi- 
cient cause."  We  have  found  out  which  are  essential 
and  which  are  accidental  antecedents,  and  estab- 
lished possibly  what  we  may  call  the  law  of  succes- 
sion, but  nothing  more.  There  may  be  a  whole  chain 
of  such  antecedents — we  frequently  know  that  there 
is — and,  behind  all,  the  true  cause  as  much  concealed 
as  ever.  The  mind,  moreover,  refuses  to  stop  at  this 
point,  or  to  rest  satisfied  with  such  a  result.  It  at 
once  begins  to  theorize.  Why  is  it  that  a  difference 
of  temperature  causes  the  steam  engine  to  work,  or 
the  radiometer  wheel  of  our  illustration  to  turn  ?  We 
cannot  answer  the  question  with  certainty,  but  this 
is  our  theory : 

"  Heat  is  a  mode  of  motion,'*  and  its  phenomena 
are  the  effects  of  the  motion  of  molecules  of  matter. 
Molecules,  although  of  an  order  of  magnitude  far 
removed  from  our  limits  of  perception,  are  as  real 
masses  as  cannon-balls  or  bullets,  and  their  motions 
as  rapid  and  as  real,  and  although  the  moving  power 
of  single  molecules  is  as  nothing,  yet  collectively 
their  motion  is  capable  of  producing  effects  com- 
pared with  which  the  mightiest  bombardment  is  in- 
significant. 

Now,  although  the  air  has  been  exhausted  to  a 
very  high  degree  from  the  bulb  of  the  radiometer, 
the  interior  still  contains  a  vast  number  of  mole- 
cules of  gas,  which,  unless  our  calculations  are  great- 
ly at  fault,  must  be  counted  by  the  million  miUion 
for  every  cubic  inch  of  capacity.  Moreover,  at  the 
degree  of  exhaustion  reached  in  the  bulb,  the  am- 
plitude of  the  motion  of  the  little  masses  becomes 


MOLECULAR  THEORY.  317 

SO  considerable  that  they  bound  to  and  fro  between 
the  vanes  of  the  wheel  and  the  surface  of  the  inclos- 
ing glass,  and  according  to  our  theory  the  motion  of 
the  wheel  is  the  result  of  this  reaction.  This  theory  is 
supported  by  the  fact  that  if  we  exhaust  the  air  from 
the  bulb  of  the  instrument  beyond  a  certain  limit  we 
arrest  the  motion.  It  is  also  true,  however,  that  the 
motion  stops  if  the  amount  of  air  be  only  slightly  in- 
creased, for  the  evident  reason  that  there  is  then  less 
free  room  for  the  motion  of  the  separate  molecules, 
and  they  do  not  move  far  enough  to  cause  any  re- 
action between  the  wheel  and  the  surrounding  walls. 

To  those  who  have  become  familiar  with  the  con- 
ception of  molecular  magnitudes  this  theory  is  very 
plausible.  If  you  ask  whether  the  theory  is  true,  I 
can  only  answer  that  we  may  perhaps  regard  it  as 
relatively  true,  seeing  that  it  has  explained  a  great 
many  facts  and  suggested  lines  of  investigation  which 
have  led  to  new  discoveries.  But  it  certainly  is  not 
absolutely  true  in  the  sense  of  expressing  the  whole 
truth.  These  molecules  are  creatures  of  the  scientific 
imagination,  and  may  be  mere  fictions,  but  the  value  . 
of  the  theory  lies  in  its  power  of  directing  research, 
and,  as  I  have  before  said,  I  believe  that  all  theories 
which  have  this  power  are  partial  truths;  but  no 
one  can  regard  them  as  perfect  representations  of 
the  realities  of  nature.  Men  who,  in  the  first  flush 
of  discovery,  feel  the  guiding  power  of  a  theory, 
are  wont  to  associate  with  it  an  undue  reality,  but 
they  soon  learn  their  error  by  experience. 

What  we  have  just  said  is  true  of  all  the  great 
theories  of  science,  but  it  is  especially  true  of  that 


3l8  MOLECULAR  THEORY. 

form  of  the  atomic  theory  which  is  now  the  chief 
guide  in  chemical  investigation. 

The  chemist  is  acquainted  with  numerous  groups 
of  substances  which  we  call  isomeric  compounds,  and 
two  substances  are  said  to  be  isomeric  when  they  not 
only  consist  of  the  same  elements  united  in  the  same 
proportions,  but  also  have  the  same  density  in  the 
state  of  vapor,  so  that  according  to  the  molecular 
theory  their  molecules  must  have  the  same  weight. 
For  example,  the  two  substances  called  butyric  acid 
and  acetic  ether  are  isomeric  bodies.  The  vapor 
density,  as  we  call  it,  of  both  substances  is  forty- 
four  times  that  of  hydrogen,  and  they  both  consist 
of  carbon,  hydrogen,  and  oxygen  united  in  precisely 
the  same  proportions,  yet  the  two  substances  differ 
from  each  other  in  their  properties  most  widely. 
Butyric  acid  is  an  oily  liquid,  with  whose  offensive 
smell  we  are  only  too  familiar,  since  it  is  the  notice- 
able ingredient  of  rancid  butter.  It  does  not  boil 
until  the  temperature  reaches  302°  on  our  Fahrenheit 
scale,  and  does  not  readily  inflame.  Acetic  ether, 
on  the  other  hand,  is  a  limpid  liquid  with  a  pleasant 
fruity  smell,  highly  volatile,  boiling  at  165'^,  and 
inflaming  with  the  greatest  ease.  What,  now,  is 
the  cause  of  this  most  marked  difference?  The 
phenomenon  demands  an  explanation,  and  invites 
theorizing,  and  the  theory  we  have  formed  is  as 
follows : 

The  molecules  of  all  compound  substances  are 
themselves  groups  of  elementary  atoms,  and  the 
molecules  of  two  isomeric  compounds,  Hke  butyric 
acid  and  acetic  ether,  although  consisting  of  the 


STRUCTURAL  SYMBOLS.  319 

same  number  of  the  same  atoms,  and  therefore  hav- 
ing the  same  weight,  differ  from  each  other  in  that 
these  atoms  are  differently  grouped.  Nay,  we  go 
much  further  than  this,  for  we  have  formed  a  scheme 
of  the  manner  in  which  the  atoms  are  grouped  in 
each  case,  thus : 

OHHH        HH   OH 

I  I   I    I    I  II      Ml 

H-0-C-C-C-C-H    H-C-C-0-C-C-H 

ill  II      I 

HHH        HH     H 

Butyric  Acid.  Acetic  Ether. 

In  these  diagrams  the  capitals  stand  for  atoms  of 
the  elementary  substances  of  whose  names  they  are 
the  initial  letters,  and  it  is  obvious  that  not  only  two 
isomeric  compounds,  but  a  great  number,  might  be 
formed  by  differently  grouping  these  same  atoms ; 
although  the  number  of  possible  combinations  is 
greatly  diminished  by  conditions  imposed  by  well- 
known  chemical  principles,  which  it  would  be  out  of 
place  to  discuss  in  this  connection.  Our  diagrams, 
moreover,  indicate  a  great  deal  more  than  the  gene- 
ral theory,  that  the  differences  between  isomeric 
compounds  depend  on  differences  in  the  grouping 
of  the  same  atoms  ;  for  the  exact  grouping  in  each 
case  is  based  on  the  known  chemical  relations  of  the 
substances.  There  is  a  reason  for  the  position  of 
each  letter  in  these  structural  symbols,  as  they  are 
called. 

We  have  here  given  one  of  the  simplest  illustrations 


320  WORKING  THEORIES. 

of  the  theory  of  molecular  structure  which  is  the  basis 
of  modern  theoretical  chemistry.  It  is  the  chief 
object  of  chemical  investigation  at  the  present  time 
to  discover  the  molecular  structure  of  chemical  com- 
pounds, and  there  is  frequently  as  earnest  discussion 
about  the  position  of  a  letter  in  one  of  these  struct- 
ural symbols  as  there  is  in  natural  history  about  the 
origin  of  species  ;  and  if  there  were  a  point  of  theo- 
logical doctrine  involved  in  the  controversy,  the  dis- 
cussion w^ould  be  doubtless  as  personal  and  as  bitter. 
Yet  no  one  in  his  sober  senses  dreams  that  these 
diagrams  represent  realities.  If  there  are  such 
things  as  atoms  and  molecules,  all  analogy  would 
lead  us  to  believe  that  the  parts  must  sustain  rela- 
tions to  the  whole  similar  to  those  of  the  members 
of  the  solar  system,  and  like  the  sun  and  planets 
must  have  their  orbits  and  periods  of  revolution. 
Still  our  diagrams  give  us  correct  representations 
of  the  relations  between  a  large  number  of  facts 
which  they  serve  to  group  together,  and  this  theory 
of  molecular  structure  has  been  one  of  the  most 
successful  aids  in  directing  investigation  which  science 
has  known.  It  has  led  to  the  discovery  of  a  process 
of  manufacturing  artificially  the  valuable  madder 
dye  called  alizarine — a  discovery  which  has  revolu- 
tionized one  of  the  most  important  industries  of  the 
world — and  this  is  but  one  of  hundreds  of  new  dis- 
coveries with  which  it  has  enriched  the  arts  of  life 
or  extended  chemical  science.  In  a  word,  it  has 
been  a  most  valuable  "working  theory,"  and  no 
other  theory  except  the  law  of  gravitation  can  be 
compared  with  it  in  efficiency.     Hence,  absurd  as  our 


WORKING  THEORIES.  321 

conceptions  of  molecular  structure  certainly  would 
be,  if  we  supposed  them  realized  in  the  crude  forms 
which  our  diagrams  suggest,  yet  we  cannot  but  re- 
gard these  representations  as  the  rude  symbols 
of  a  real  truth  which  in  its  essence  transcends  the 
limits  of  our  present  knowledge.  That  which  is  true 
of  the  molecular  theory  of  modern  chemistry  is 
equally  true  of  the  two  great  conceptions  which  are 
always  cited  as  examples  of  the  most  perfect  theo- 
ries of  physical  science.  The  undulatory  theory  of 
light  involves  assumptions  in  regard  to  the  alleged 
ether  which  are  simply  preposterous,  and  even  the 
law  of  gravitation  takes  for  granted  action  at  a 
distance  which  is  opposed  to  all  experience  and  to 
all  philosophical  thought.  Still,  to  abandon  these 
theories,  because  we  cannot  accept  their  postulates, 
would  be  as  foolish  as  to  throw  away  our  compass 
because  we  cannot  agree  about  the  theory  of  mag- 
netism. 

Now  we  are  told  by  the  naturalists  that  Darwin- 
ism is  just  such  another  working  theory,  and  they 
are,  with  reason,  impatient  when  blamed  for  follow- 
ing its  guidance  because  it  cannot  be  recon- 
ciled with  certain  cherished  theological  dogmas. 
And,  assuming  that  the  dogmas  are  right,  you 
might  as  reasonably  find  fault  with  the  mari- 
ner for  using  the  magnetic  needle,  because  it  does 
not  always  point  to  the  true  north.  Like  the 
needle,  our  theory  points  out  the  path  of  discovery, 
and,  although  the  way  may  at  times  seem  to  lead 
backward,  and  men,  like  Columbus,  may  become 
frightened  at  the  evident  aberrations  of  their  guide, 
14* 


322  DOGMATISM   IN   SCIENCE. 

yet  if,  with  the  brave  navigator,  they  persevere,  the 
trusted  guide  will  certainly  conduct  them  to  the  true 
goal  in  the  end,  unless  truth  is  a  fiction,  and  the 
whole  issue  of  the  human  faculties  a  lie.  Neverthe- 
less there  may  be  as  blind  dogmatism  in  science  as 
has  ever  existed  in  theology,  and  it  is  dogmatism 
when  men  claim  as  absolute  certainty  what  is  at 
most  merely  relative  truth,  and  treat  with  supercil- 
iousness all  who  do  not  accept  their  authority  as  fi- 
nal. Certainly,  let  us  be  true  to  our  convictions,  and 
hold  fast  to  our  theories  as  the  earthen  vessels  which 
contain  a  precious  treasure,  but  let  us  remember, 

Our  little  systems  have  their  day  ; 

They  have  their  day  and  cease  to  be ; 

They  are  but  broken  lights  of  thee,       : 
And  thou,  O  Lord,  art  more  than  they. 

Such,  then,  being  the  credentials,  and  such  the 
methods  of  science,  let  us  turn  for  a  few  moments  to 
the  credentials  and  methods  of  theology,  and  ask,  in 
all  humility,  whether  the  conditions  do  not  impose 
limits  on  human  thought  in  this  direction  as  well  as 
in  the  other.  In  theology,  as  in  science,  there  are 
certain  facts  which,  although  chiefly  facts  of  con- 
sciousness, and  not  facts  of  observation,  are  no  less 
facts  than  the  phenomena  of  nature.  Prominent 
among  these  facts  are  the  moral  judgments,  the 
affections,  and  the  aspirations  of  the  soul,  which, 
explain  them  as  you  will,  are  the  most  important 
factors  of  human  life — the  most  potent  agents  in 
human  society.  Corresponding  to  these  affections 
and  aspirations  are  certain  religious  beliefs  which  we 


THEOLOGICAL  DATA.  323 

have  inherited  from  our  ancestors,  and  which  have 
come  down  to  us  with  the  authority  of  eighteen  cen- 
turies of  human  experience.  During  that  period 
these  beHefs  have  satisfied  the  highest  aspirations  of 
humanity,  and  have  led  many  of  the  purest  and  no- 
blest men  whom  the  world  has  known  to  encounter 
peril,  endure  cruel  torments,  and  suffer  ignominious 
death,  in  attestation  of  their  faith.  The  origin  of 
this  faith  was  a  life  which,  as  portrayed  to  us  in  the 
Gospels,  has  aroused  in  every  generation  of  men  from 
its  birth  the  noblest  enthusiasm  and  the  warmest 
love ;  a  life  which  has  appeared  more  and  more 
transcendent  as  civilization  has  advanced,  and  which 
has  been  the  one  power  that  has  redeemed  man  from 
his  selfishness,  and  enthroned  charity  among  the 
chief  rulers  of  the  earth.  Such,  then,  are  the  cre- 
dentials of  Christianity — a  real  want,  an  adequate 
satisfaction.  Learned  men  have  endeavored  to  for- 
mulate the  principles  of  religious  beliefs,  and  hence 
have  come  systems  of  theology,  in  regard  to  which 
we  might  repeat  very  nearly  the  same  statements 
that  we  have  already  made  in  regard  to  the  theories 
of  science.  These  systems  have  certainly  satisfied 
the  great  mass  of  mankind,  and  have  done  a  good 
work  in  defining  and  preserving  the  faith  ;  but  they 
are  all  earthen  vessels,  and,  like  the  working  theories 

of  science, 

"  half  reveal 
And  half  conceal  the  soul  within." 

Let  us  remember  that  as  Christianity  was  revealed 
in  a  life,  it  ever  abides  as  a  life  in  the  heart  of  the 
believer,  and  only  those  who  have  lived  that  life  can 


324  METHODS   OF  THEOLOGY. 

know  how  real  it  is.  To  all  such,  however,  it  is  the 
most  real  thing  in  the  world,  and  the  theological 
forms  in  which  it  finds  expression  have  the  same 
reason  for  their  being  as  the  forms  of  science,  and 
are  held  the  more  sacred  as  the  truths  symbolized 
are  the  more  dearly  cherished.  Moreover,  it  is  a 
fact  most  worthy  of  notice,  that  Christianity  is 
almost  co-extensive  with  civilization,  or,  as  Cole- 
ridge has  expressed  it,  "  Christendom  is  the  best  evi- 
dence of  Christianity." 

While,  however,  the  "internal  evidences"  of  Chris- 
tianity, which  we  may  not  inappropriately  call  the 
credentials  of  theology,  are  so  similar  to  the  creden- 
tials of  physical  science,  the  methods  of  theology  are, 
for  the  most  part,  utterly  unlike  the  scientific  meth- 
ods we  have  been  discussing.  In  the  first  place,  the 
very  data  on  which  the  whole  body  of  Christian 
theology  rests  cannot  be  verified  by  observation. 
The  phenomena  of  nature  are  ever  with  us,  and  can 
be  closely  scrutinized  at  each  repetition  ;  but  the 
events  from  which  Christianity  arose  occurred  once 
for  all  more  than  eighteen  centuries  ago ;  and  if  we 
take  the  summary  of  those  events  given  in  the  primi- 
tive creeds  as  representing  what  is  common  to  the 
beliefs  of  the  great  body  of  Christians,  and  as  au- 
thenticated by  the  experience  of  the  Church,  and 
present  this  as  the  subject-matter  of  theology,  we 
must  claim  belief  in  these  data  on  grounds  of  faith, 
and  not  on  scientific  evidence.  We  accept  these 
supernatural  facts  not  solely  on  account  of  the  his- 
torical evidence  adduced  in  fheir  support,  but  largely 
in  deference  to  a  certain  "witness  in  our  hearts," 


METHODS   OF   THEOLOGY.  325 

which  disposes  us  to  accept  them.  To  men  who 
know  nothing  by  experience  of  this  inner  witness, 
behefs  thus  accredited  may  appear  foolishness,  and 
this  is  too  often  the  case  with  those  who,  occupied 
exclusively  with  the  study  of  nature,  are  not  accus- 
tomed to  accept  any  statement  as  true  which  cannot 
be  verified  by  experiment  or  observation,  and  who 
regard  the  order  of  nature  as  the  one  standard  from 
which  there  is  no  appeal.  On  the  other  hand,  those 
who  have  felt  its  power  are  persuaded  that  the  wit- 
ness in  themselves  is  the  voice  of  God  speaking  to 
the  heart. 

The  basis  thus  established.  Christian  theology  is 
built  up  on  the  textual  criticism,  interpretation  and 
collation  of  a  written  record,  a  form  of  study  which 
involves  historical  research,  critical  analysis,  philo- 
logical investigation,  and  metaphysical  inquiries. 
Thus  a  great  mass  of  learning  has  been  accumulated 
to  which  various  minds  will  attach  very  different 
degrees  of  value,  according  as  they  are  more  or  less 
familiar  with  the  methods  employed.  These,  how- 
ever, are  so  unlike  the  methods  of  physical  science 
that  it  would  be  the  height  of  presumption  for  a 
physicist  to  pass  any  judgment  on  the  results. 
But  certainly  no  one  can  claim  for  them  a  greater 
value  than  for  the  best  working  theories  of  science. 

Seeing,  then,  that  the  limits  of  positive  knowledge 
are  so  well  defined,  both  in  natural  science  and  in 
theology,  we  certainly  need  not  be  troubled  by  the 
apparent  conflict  between  the  two  modes  of  thought, 
so  long  as  the  controversy  is  confined  to  the  debat- 
able ground  which  has  not  been   fully  explored  by 


326  RELATIVE   LIMITATIONS   OF 

either  party.  Within  the  well-explored  limits  there 
never  has  been  and  never  can  be  any  actual  disagree- 
ment, and  something  has  been  gained  if  we  have 
been  able  to  make  evident  that  such  limits  exist, 
however  imperfectly  we  have  succeeded  in  defining 
them.  The  bearing  of  such  considerations  is  ob- 
vious, and  they  lead  to  important  practical  conclu- 
sions. In  the  first  place,  they  should  teach  men  of 
science  to  honor  and  reverence  the  forms  of  religion. 
They  are  the  types  and  symbols  of  a  truth  higher  than 
any  which  Science  can  teach.  Let  Science  vindicate 
her  own  methods,  and  allow  no  interference  within 
her  proper  sphere ;  but  unless  she  learn  that  there 
are  other  sources  of  knowledge  than  material  nature, 
and  other  channels  of  truth  than  the  intellect,  her 
own  philosophy  will  be  confounded,  and  her  light 
will  go  out  in  darkness.  On  the  other  hand,  it  is 
equally  the  duty  of  the  ministers  of  religion  to  honor 
and  respect  the  methods  of  science.  They  have 
been  ordained  by  God,  and  through  these  processes 
of  thought  He  is  constantly  revealing  eternal  truths 
to  the  mind  of  man.  Insist  as  strongly  as  you  please 
that  Science  should  be  allowed  no  voice  in  matters 
of  faith.  Scrutinize  as  closely  as  you  can  every  step 
of  her  logic ;  but  so  long  as  she  keeps  within  her 
legitimate  province,  allow  her  the  largest  liberty, 
and  extend  to  her  the  most  generous  encourage- 
ment. Watch  sharply  her  results,  and  expose  her 
fallacies  wherever  you  can  find  them ;  but  if  your 
judgment  condemns,  let  it  be  on  scientific  grounds, 
and  not  by  any  arbitrary  standard  of  your  own. 
Above  all,  even  if  you  think  your  most  cherished 


SCIENTIFIC  AND   RELIGIOUS   THOUGHT.       327 

Opinions  are  in  danger,  do  not  withdraw  your  fellow- 
ship hastily,  or  be  betrayed  into  undiscriminating 
censure.  Science  is  paramount  within  her  own  prov- 
ince. Do  everything  in  your  power  to  consecrate 
her  aims  and  sanctify  her  spirit,  but  do  not  attempt 
to  control  her  investigations  or  restrict  her  free 
thought.  Await  God's  time.  If  Science  be  wrong, 
she  will  sooner  or  later  correct  her  error.  If  she  be 
right,  the  *^  Lord  of  Hosts  "  is  on  her  side,  and  you 
will  find  yourself  "  fighting  against  God." 

Again,  a  proper  appreciation  of  the  necessary  lim- 
its of  scientific  and  religious  thought  should  lead  all 
men  to  reverence  the  **  Word  of  God  "  as  it  has  been 
handed  down  to  us  through  history.  In  view  of  the 
facts  already  intimated,  I  cannot  look  with  favor  on 
any  attempts  at  Biblical  criticism  which  aim  to  square 
the  language  of  Scripture  with  the  results  of  modern 
science.  They  leave  a  most  unpleasant  impression 
on  my  mind.  Seeing  the  large  element  of  human 
ignorance,  incapacity,  and  frailty,  which  the  history 
of  both  so  conspicuously  exhibit,  I  cannot  stake  my 
faith  either  on  the  ^*  Infallibility  of  the  Church  "  or 
the  *' Infallibility  of  the  Book."  But  I  do  believe 
that  the  Bible  is  inspired  with  spiritual  truth,  from 
the  «grand  epic  of  creation,  with  which  it  opens,  to 
the  glorious  vision  of  the  New  Jerusalem  at  its 
close.  I  feel  that  its  very  words  are  consecrated  by 
the  associations  of  the  ages,  and  if  you  are  so  ready 
to  accommodate  any  part  of  them  to  the  shifting 
phases  of  science,  what  certainty  can  I  have  in  re- 
gard to  the  whole?  The  Bible  is  no  text-book  of 
science,  and  the  attempt  to  impose  an  equivocal  or 


32S  RELATIVE  LIMITATIONS  OF 

mysterious  meaning  on  its  simple  and  obvious  state- 
ments degrades  and  dishonors  it  in  the  minds  of  de- 
vout men.  The  methods  by  which  its  truths  are 
expressed  may  be  at  times  rough  and  uncouth ;  but 
they  are  the  methods  chosen  by  God,  consecrated 
by  the  blood  of  martyrs,  and  hallowed  by  the  tears 
of  saints;  and  they  have  therefore  a  power  which 
no  other  language  could  have.  Break  not  the  mould 
in  which  the  forms  of  faith  have  been  cast,  before 
they  have  become  firm  and  hard,  lest  the  precious 
metal  should  itself  be  lost.  Finally,  leave  religion 
and  science  to  their  respective  methods,  and  encour- 
age both  alike  in  their  noble  callings.  Let  science, 
by  cultivating  man's  intellect,  elevate  him  to  nobler 
and  more  spiritual  views  of  God's  wisdom  and  power. 
Let  religion,  by  purifying  man's  heart,  open  to  him 
clearer  visions  of  God's  purity  and  love;  and,  at  last, 
when  this  material  shall  have  vanished,  and  when  the 
waters  of  controversy  shall  have  ceased  to  roll,  the 
heart  and  the  intellect,  made  one  and  washed  clean 
in  the  blood  of  the  Lamb,  shall  unite  in  the  song  of 
the  angels  around  the  throne,  saying, "  Blessing,  and 
glory,  and  wisdom,  and  thanksgiving,  and  honor,  and 
power,  and  might,  be  unto  our  God  for  ever  and  ever." 
But  while  insisting  upon  the  necessary  limitations 
of  scientific  and  religious  thought,  I  must  not  forget 
that  all  such  considerations  bear  with  peculiar  force 
upon  the  questions  I  have  discussed  in  this  book. 
Therefore,  although  I  have  most  carefully  endeav- 
ored to  guard  my  argument  from  the  slighest  ex- 
aggeration, I  should  not  feel  justified  in  concluding 
without  distinctly  stating  how  far,  in  my  opinion, 


SCIENTIFIC  AND  RELIGIOUS  THOUGHT.       329 

the  argument  of  natural  theology  may  be  safely 
carried,  and  to  what  extent  unaided  science  may 
be  said  really  to  prove  the  fundamental  truths  of 
Christianity. 

In  the  first  place,  then,  I  believe  that  the  exist- 
ence of  an  intelligent  Author  of  nature,  infinite  in 
wisdom  and  absolute  in  power,  may  be  proved  from 
the  phenomena  of  the  material  world  with  as  much 
certainty  as  can  be  any  theory  of  science.  In  the 
second  place,  I  am  of  opinion  that  the  facts  of  na- 
ture are  throughout  consistent  with  the  belief  that 
the  Author  of  nature  is  a  personal  being,  and  the 
one  only  and  true  God  revealed  to  us  in  the  Bible. 
Lastly,  I  think  that  the  relations  of  the  human 
mind  to  the  material  world,  viewed  in  the  light  of 
modern  science,  give  us  strong  reason  to  believe,  on 
scientific  grounds  alone,  that  the  universe  is  still 
sustained  in  all  its  parts  by  the  same  omnipotent 
and  omniscient  Will  which  first  called  it  into  being. 

To  the  extent  I  have  indicated,  I  regard  the  argu- 
ment of  natural  theology  as  logically  valid.  More- 
over, I  am  persuaded  that  science  confirms  and 
illustrates  the  priceless  truth  which  Christ  came 
on  earth  to  reveal ;  but  I  do  not  believe  that  the 
unaided  intellect  of  man  could  ever  have  been 
assured  of  even  the  least  of  these  truths  independ- 
ently of  revelation.  And,  as  I  stated  in  my  intro- 
ductory chapter,  I  feel  that  the  best  service  which 
science  can  render  to  religion  is  in  the  way  of  con- 
firmation and  illustration,  rather  than  in  that  of  ab- 
solute proof,  and  for  this  reason  I  have  preferred  to 
discuss  my  subject  chiefly  from  that  point  of  view. 


330  VALIDITY  OF  THE  ARGUMENT. 

The  subject,  as  prescribed  by  the  founder  of  the 
"  Graham  Lectures,"  ^  was  ''  The  power,  wisdom,  and 
goodness  of  God  as  manifested  in  His  works,"  and  to 
this  form  of  statement,  if  interpreted  in  the  sense  just 
indicated,  I  have  nothing  to  object.  I  do  not  beheve, 
however,  in  any  sense,  that  nature  proves  the  good- 
ness of  God.  When  the  heart  has  been  once  touched 
by  the  love  of  God,  as  manifested  on  Calvary,  the  to- 
kens of  God's  goodness  are  visible  everywhere ;  but 
before  this,  nature,  to  one  who  has  seen  its  terrors 
and  felt  its  power,  looks  dark  indeed  ;  and  the  pre- 
tence that  the  material  universe,  unexplained  by 
revelation,  manifests  a  God  of  unmixed  beneficence, 
not  only  does  harm  to  religion,  but  places  science 
in  a  false  light.  The  most  superficial  observation 
shows  that  this  is  not  true.  Lightning  and  tem- 
pest, plague,  pestilence,  and  famine,  with  all  their 
awful  accompaniments,  are  no  less  facts  of  nature 
than  the  golden  sunset,  the  summer's  breeze,  and 
the  ripening  harvest ;  and  who  does  not  "  know  that 
the  whole  creation  groaneth  and  travaileth  in  pain 
together  until  now"?  It  does  not  change  the 
terrible  fact  to  say  that  nature  has  been  disordered 
by  man's  sin  ;  for  sin  is  itself  the  greatest  evil  in  the 
world,  and  its  ghastly  forms  meet  us  at  every  step. 
So  prominent,  indeed,  is  the  evil  in  nature,  and  so 
insidiously  and  mysteriously  does  it  pervade  the 
whole  system,  that  an  argument  to  prove  the  ma- 
lignity of  God  could  be  made  to  appear  quite  as 
plausible   as   the    arguments  which    are  frequently 

*  See  ''  Preface  to  First  Edition." 


CONCLUSION.  331 


urged  to  prove  His  pure  beneficence ;  and  when 
the  unaided  human  intellect  has  attempted  to  make 
to  itself  a  beneficent  God,  it  has  usually  made  a 
malignant  deity  as  well.  Nature  seems  to  manifest 
God's  wrath  no  less  than  His  love,  and  it  is  a  false 
and  sickly  philosophy  which  attempts  to  keep  the 
awful  fact  out  of  sight.  God  is  our  Father ;  but 
nature  could  not  teach  it,  and  **  the  Word  was  made 
flesh  "  to  declare  it.  God  is  love  ;  but  nature  could 
not  prove  it,  and  the  Lamb  was  "  slain  from  the 
foundation  of  the  world"  to  attest  it.  Nature  is 
but  a  part  of  God's  system,  and  not  until  the  natural 
and  the  supernatural  shall  be  made  one  will  the  mys- 
tery of  evil  be  solved. 


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